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	$172.32	11.280%	$191.7577	$191.76	$191.75	$191.80
Purchase #2	$228.75	10.744%	$253.3269	$253.33	$253.35	$253.30
Purchase #3	$56.25	5.594%	$59.3966	$59.40	$59.40	$59.40
Purchase #4	$135.87	12.712%	$153.1418	$153.14	$153.15	$153.10
Purchase #5	$19.47	4.657%	$20.3767	$20.38	$20.40	$20.40
Purchase #6	$36.71	13.644%	$41.7187	$41.72	$41.70	$41.70
Purchase #7	$164.83	7.687%	$177.5005	$177.50	$177.50	$177.50
7 purchase totals =	$814.20		$897.2189	$897.23	$897.25	$897.20