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	$148.59	11.409%	$165.5426	$165.54	$165.55	$165.50
Purchase #2	$137.69	12.606%	$155.0472	$155.05	$155.05	$155.00
Purchase #3	$156.32	9.478%	$171.136	$171.14	$171.15	$171.10
Purchase #4	$48.85	7.816%	$52.6681	$52.67	$52.65	$52.70
Purchase #5	$11.67	7.435%	$12.5377	$12.54	$12.55	$12.50
Purchase #6	$223.90	8.842%	$243.6972	$243.70	$243.70	$243.70
Purchase #7	$233.27	3.866%	$242.2882	$242.29	$242.30	$242.30
7 purchase totals =	$960.29		$1,042.9170	$1,042.93	$1,042.95	$1,042.80