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	$173.54	3.629%	$179.8378	$179.84	$179.85	$179.80
Purchase #2	$90.82	6.167%	$96.4209	$96.42	$96.40	$96.40
Purchase #3	$103.55	7.579%	$111.3981	$111.40	$111.40	$111.40
Purchase #4	$59.78	8.581%	$64.9097	$64.91	$64.90	$64.90
Purchase #5	$64.65	11.365%	$71.9975	$72.00	$72.00	$72.00
Purchase #6	$71.74	6.309%	$76.2661	$76.27	$76.25	$76.30
Purchase #7	$109.87	12.581%	$123.6927	$123.69	$123.70	$123.70
7 purchase totals =	$673.95		$724.5228	$724.53	$724.50	$724.50