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	$202.75	12.689%	$228.4769	$228.48	$228.50	$228.50
Purchase #2	$160.74	7.332%	$172.5255	$172.53	$172.55	$172.50
Purchase #3	$224.47	4.202%	$233.9022	$233.90	$233.90	$233.90
Purchase #4	$57.83	9.532%	$63.3424	$63.34	$63.35	$63.30
Purchase #5	$102.81	3.513%	$106.4217	$106.42	$106.40	$106.40
Purchase #6	$31.78	4.555%	$33.2276	$33.23	$33.25	$33.20
Purchase #7	$240.47	13.844%	$273.7607	$273.76	$273.75	$273.80
7 purchase totals =	$1,020.85		$1,111.6570	$1,111.66	$1,111.70	$1,111.60