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	$144.57	10.806%	$160.1922	$160.19	$160.20	$160.20
Purchase #2	$55.57	4.378%	$58.0029	$58.00	$58.00	$58.00
Purchase #3	$159.44	12.516%	$179.3955	$179.40	$179.40	$179.40
Purchase #4	$40.69	11.355%	$45.3103	$45.31	$45.30	$45.30
Purchase #5	$157.83	10.817%	$174.9025	$174.90	$174.90	$174.90
Purchase #6	$209.46	11.389%	$233.3154	$233.32	$233.30	$233.30
Purchase #7	$216.30	7.786%	$233.1411	$233.14	$233.15	$233.10
7 purchase totals =	$983.86		$1,084.2599	$1,084.26	$1,084.25	$1,084.20