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	$229.62	6.190%	$243.8335	$243.83	$243.85	$243.80
Purchase #2	$227.37	3.715%	$235.8168	$235.82	$235.80	$235.80
Purchase #3	$41.87	3.310%	$43.2559	$43.26	$43.25	$43.30
Purchase #4	$65.97	12.644%	$74.3112	$74.31	$74.30	$74.30
Purchase #5	$165.27	12.743%	$186.3304	$186.33	$186.35	$186.30
Purchase #6	$119.58	4.104%	$124.4876	$124.49	$124.50	$124.50
Purchase #7	$92.78	8.454%	$100.6236	$100.62	$100.60	$100.60
7 purchase totals =	$942.46		$1,008.6590	$1,008.66	$1,008.65	$1,008.60