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	$43.61	7.427%	$46.8489	$46.85	$46.85	$46.80
Purchase #2	$62.54	3.566%	$64.7702	$64.77	$64.75	$64.80
Purchase #3	$247.44	7.242%	$265.3596	$265.36	$265.35	$265.40
Purchase #4	$125.37	11.580%	$139.8878	$139.89	$139.90	$139.90
Purchase #5	$249.91	5.660%	$264.0549	$264.05	$264.05	$264.10
Purchase #6	$209.70	9.730%	$230.1038	$230.10	$230.10	$230.10
Purchase #7	$153.41	13.793%	$174.5698	$174.57	$174.55	$174.60
7 purchase totals =	$1,091.98		$1,185.5950	$1,185.59	$1,185.55	$1,185.70