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	$55.36	3.517%	$57.307	$57.31	$57.30	$57.30
Purchase #2	$182.26	7.768%	$196.418	$196.42	$196.40	$196.40
Purchase #3	$158.31	13.874%	$180.2739	$180.27	$180.25	$180.30
Purchase #4	$202.38	4.501%	$211.4891	$211.49	$211.50	$211.50
Purchase #5	$149.47	12.352%	$167.9325	$167.93	$167.95	$167.90
Purchase #6	$155.52	6.504%	$165.635	$165.64	$165.65	$165.60
Purchase #7	$167.26	12.777%	$188.6308	$188.63	$188.65	$188.60
7 purchase totals =	$1,070.56		$1,167.6863	$1,167.69	$1,167.70	$1,167.60