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	$187.82	9.573%	$205.8	$205.80	$205.80	$205.80
Purchase #2	$79.64	11.666%	$88.9308	$88.93	$88.95	$88.90
Purchase #3	$56.70	8.446%	$61.4889	$61.49	$61.50	$61.50
Purchase #4	$201.27	13.713%	$228.8702	$228.87	$228.85	$228.90
Purchase #5	$36.25	11.708%	$40.4942	$40.49	$40.50	$40.50
Purchase #6	$32.91	7.860%	$35.4967	$35.50	$35.50	$35.50
Purchase #7	$62.85	13.146%	$71.1123	$71.11	$71.10	$71.10
7 purchase totals =	$657.44		$732.1931	$732.19	$732.20	$732.20