Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$225.83	3.494%	$233.7205	$233.72	$233.70	$233.70
Purchase #2	$124.30	11.269%	$138.3074	$138.31	$138.30	$138.30
Purchase #3	$91.46	10.718%	$101.2627	$101.26	$101.25	$101.30
Purchase #4	$160.57	7.233%	$172.184	$172.18	$172.20	$172.20
Purchase #5	$133.44	5.474%	$140.7445	$140.74	$140.75	$140.70
Purchase #6	$157.84	7.264%	$169.3055	$169.31	$169.30	$169.30
Purchase #7	$141.71	10.376%	$156.4138	$156.41	$156.40	$156.40
7 purchase totals =	$1,035.15		$1,111.9384	$1,111.93	$1,111.90	$1,111.90