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	$88.39	3.150%	$91.1743	$91.17	$91.15	$91.20
Purchase #2	$147.76	10.377%	$163.0931	$163.09	$163.10	$163.10
Purchase #3	$151.33	11.607%	$168.8949	$168.89	$168.90	$168.90
Purchase #4	$231.67	8.282%	$250.8569	$250.86	$250.85	$250.90
Purchase #5	$209.53	13.417%	$237.6426	$237.64	$237.65	$237.60
Purchase #6	$191.71	10.747%	$212.3131	$212.31	$212.30	$212.30
Purchase #7	$78.82	10.288%	$86.929	$86.93	$86.95	$86.90
7 purchase totals =	$1,099.21		$1,210.9039	$1,210.89	$1,210.90	$1,210.90