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	$143.26	6.235%	$152.1923	$152.19	$152.20	$152.20
Purchase #2	$99.85	13.626%	$113.4556	$113.46	$113.45	$113.50
Purchase #3	$250.26	10.741%	$277.1404	$277.14	$277.15	$277.10
Purchase #4	$32.90	9.584%	$36.0531	$36.05	$36.05	$36.10
Purchase #5	$118.54	6.778%	$126.5746	$126.57	$126.55	$126.60
Purchase #6	$196.99	11.619%	$219.8783	$219.88	$219.90	$219.90
Purchase #7	$167.59	10.870%	$185.807	$185.81	$185.80	$185.80
7 purchase totals =	$1,009.39		$1,111.1013	$1,111.10	$1,111.10	$1,111.20