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	$170.39	10.727%	$188.6677	$188.67	$188.65	$188.70
Purchase #2	$168.72	12.564%	$189.918	$189.92	$189.90	$189.90
Purchase #3	$222.56	3.121%	$229.5061	$229.51	$229.50	$229.50
Purchase #4	$169.89	9.224%	$185.5607	$185.56	$185.55	$185.60
Purchase #5	$134.33	12.847%	$151.5874	$151.59	$151.60	$151.60
Purchase #6	$169.87	13.795%	$193.3036	$193.30	$193.30	$193.30
Purchase #7	$210.43	8.785%	$228.9163	$228.92	$228.90	$228.90
7 purchase totals =	$1,246.19		$1,367.4598	$1,367.47	$1,367.40	$1,367.50