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	$249.77	4.512%	$261.0396	$261.04	$261.05	$261.00
Purchase #2	$48.64	11.760%	$54.3601	$54.36	$54.35	$54.40
Purchase #3	$152.84	8.420%	$165.7091	$165.71	$165.70	$165.70
Purchase #4	$52.38	13.378%	$59.3874	$59.39	$59.40	$59.40
Purchase #5	$173.49	3.676%	$179.8675	$179.87	$179.85	$179.90
Purchase #6	$102.83	11.547%	$114.7038	$114.70	$114.70	$114.70
Purchase #7	$163.99	12.562%	$184.5904	$184.59	$184.60	$184.60
7 purchase totals =	$943.94		$1,019.6579	$1,019.66	$1,019.65	$1,019.70