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	$204.50	8.689%	$222.269	$222.27	$222.25	$222.30
Purchase #2	$62.71	5.507%	$66.1634	$66.16	$66.15	$66.20
Purchase #3	$109.52	7.272%	$117.4843	$117.48	$117.50	$117.50
Purchase #4	$88.46	3.275%	$91.3571	$91.36	$91.35	$91.40
Purchase #5	$28.64	12.628%	$32.2567	$32.26	$32.25	$32.30
Purchase #6	$147.91	5.675%	$156.3039	$156.30	$156.30	$156.30
Purchase #7	$180.41	8.640%	$195.9974	$196.00	$196.00	$196.00
7 purchase totals =	$822.15		$881.8318	$881.83	$881.80	$882.00