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	$44.27	6.517%	$47.1551	$47.16	$47.15	$47.20
Purchase #2	$62.65	7.846%	$67.5655	$67.57	$67.55	$67.60
Purchase #3	$82.31	4.396%	$85.9283	$85.93	$85.95	$85.90
Purchase #4	$59.87	11.839%	$66.958	$66.96	$66.95	$67.00
Purchase #5	$196.43	9.219%	$214.5389	$214.54	$214.55	$214.50
Purchase #6	$212.85	10.784%	$235.8037	$235.80	$235.80	$235.80
Purchase #7	$168.35	6.714%	$179.653	$179.65	$179.65	$179.70
7 purchase totals =	$826.73		$897.6025	$897.61	$897.60	$897.70