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	$229.96	10.224%	$253.4711	$253.47	$253.45	$253.50
Purchase #2	$136.38	5.689%	$144.1387	$144.14	$144.15	$144.10
Purchase #3	$20.43	3.831%	$21.2127	$21.21	$21.20	$21.20
Purchase #4	$54.71	8.777%	$59.5119	$59.51	$59.50	$59.50
Purchase #5	$112.72	9.827%	$123.797	$123.80	$123.80	$123.80
Purchase #6	$225.32	8.718%	$244.9634	$244.96	$244.95	$245.00
Purchase #7	$79.37	11.696%	$88.6531	$88.65	$88.65	$88.70
7 purchase totals =	$858.89		$935.7479	$935.74	$935.70	$935.80