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	$137.72	9.544%	$150.864	$150.86	$150.85	$150.90
Purchase #2	$167.55	7.553%	$180.2051	$180.21	$180.20	$180.20
Purchase #3	$122.47	7.629%	$131.8132	$131.81	$131.80	$131.80
Purchase #4	$111.55	12.399%	$125.3811	$125.38	$125.40	$125.40
Purchase #5	$54.63	9.265%	$59.6915	$59.69	$59.70	$59.70
Purchase #6	$113.97	4.104%	$118.6473	$118.65	$118.65	$118.60
Purchase #7	$120.25	5.251%	$126.5643	$126.56	$126.55	$126.60
7 purchase totals =	$828.14		$893.1665	$893.16	$893.15	$893.20