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	$97.33	8.657%	$105.7559	$105.76	$105.75	$105.80
Purchase #2	$149.88	4.595%	$156.767	$156.77	$156.75	$156.80
Purchase #3	$176.57	11.496%	$196.8685	$196.87	$196.85	$196.90
Purchase #4	$216.93	11.488%	$241.8509	$241.85	$241.85	$241.90
Purchase #5	$176.48	3.647%	$182.9162	$182.92	$182.90	$182.90
Purchase #6	$48.80	4.152%	$50.8262	$50.83	$50.85	$50.80
Purchase #7	$152.65	13.400%	$173.1051	$173.11	$173.10	$173.10
7 purchase totals =	$1,018.64		$1,108.0898	$1,108.11	$1,108.05	$1,108.20