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	$226.96	8.226%	$245.6297	$245.63	$245.65	$245.60
Purchase #2	$37.85	10.681%	$41.8928	$41.89	$41.90	$41.90
Purchase #3	$107.96	8.454%	$117.0869	$117.09	$117.10	$117.10
Purchase #4	$250.49	11.637%	$279.6395	$279.64	$279.65	$279.60
Purchase #5	$189.69	10.661%	$209.9129	$209.91	$209.90	$209.90
Purchase #6	$64.75	11.321%	$72.0803	$72.08	$72.10	$72.10
Purchase #7	$43.40	6.115%	$46.0539	$46.05	$46.05	$46.10
7 purchase totals =	$921.10		$1,012.2960	$1,012.29	$1,012.35	$1,012.30