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	$183.25	12.273%	$205.7403	$205.74	$205.75	$205.70
Purchase #2	$85.88	8.316%	$93.0218	$93.02	$93.00	$93.00
Purchase #3	$37.76	12.664%	$42.5419	$42.54	$42.55	$42.50
Purchase #4	$170.89	11.290%	$190.1835	$190.18	$190.20	$190.20
Purchase #5	$162.74	7.119%	$174.3255	$174.33	$174.35	$174.30
Purchase #6	$247.45	11.401%	$275.6618	$275.66	$275.65	$275.70
Purchase #7	$106.54	4.307%	$111.1287	$111.13	$111.15	$111.10
7 purchase totals =	$994.51		$1,092.6035	$1,092.60	$1,092.65	$1,092.50