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	$82.50	5.162%	$86.7587	$86.76	$86.75	$86.80
Purchase #2	$196.31	12.624%	$221.0922	$221.09	$221.10	$221.10
Purchase #3	$127.78	11.829%	$142.8951	$142.90	$142.90	$142.90
Purchase #4	$128.63	3.443%	$133.0587	$133.06	$133.05	$133.10
Purchase #5	$135.30	12.342%	$151.9987	$152.00	$152.00	$152.00
Purchase #6	$57.69	11.204%	$64.1536	$64.15	$64.15	$64.20
Purchase #7	$146.41	13.169%	$165.6907	$165.69	$165.70	$165.70
7 purchase totals =	$874.62		$965.6477	$965.65	$965.65	$965.80