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	$105.77	5.390%	$111.471	$111.47	$111.45	$111.50
Purchase #2	$242.26	5.306%	$255.1143	$255.11	$255.10	$255.10
Purchase #3	$141.58	11.245%	$157.5007	$157.50	$157.50	$157.50
Purchase #4	$109.94	7.515%	$118.202	$118.20	$118.20	$118.20
Purchase #5	$30.63	5.490%	$32.3116	$32.31	$32.30	$32.30
Purchase #6	$106.96	11.146%	$118.8818	$118.88	$118.90	$118.90
Purchase #7	$45.30	12.475%	$50.9512	$50.95	$50.95	$51.00
7 purchase totals =	$782.44		$844.4326	$844.42	$844.40	$844.50