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	$148.65	12.695%	$167.5211	$167.52	$167.50	$167.50
Purchase #2	$241.66	13.358%	$273.9409	$273.94	$273.95	$273.90
Purchase #3	$105.45	7.266%	$113.112	$113.11	$113.10	$113.10
Purchase #4	$112.37	12.289%	$126.1791	$126.18	$126.20	$126.20
Purchase #5	$230.61	11.399%	$256.8972	$256.90	$256.90	$256.90
Purchase #6	$114.43	11.687%	$127.8034	$127.80	$127.80	$127.80
Purchase #7	$27.67	8.644%	$30.0618	$30.06	$30.05	$30.10
7 purchase totals =	$980.84		$1,095.5155	$1,095.51	$1,095.50	$1,095.50