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	$161.88	11.753%	$180.9058	$180.91	$180.90	$180.90
Purchase #2	$27.39	5.650%	$28.9375	$28.94	$28.95	$28.90
Purchase #3	$200.63	10.597%	$221.8908	$221.89	$221.90	$221.90
Purchase #4	$244.71	8.467%	$265.4296	$265.43	$265.45	$265.40
Purchase #5	$38.89	6.114%	$41.2677	$41.27	$41.25	$41.30
Purchase #6	$167.99	6.617%	$179.1059	$179.11	$179.10	$179.10
Purchase #7	$42.99	6.316%	$45.7052	$45.71	$45.70	$45.70
7 purchase totals =	$884.48		$963.2425	$963.26	$963.25	$963.20