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	$68.35	4.540%	$71.4531	$71.45	$71.45	$71.50
Purchase #2	$54.91	9.353%	$60.0457	$60.05	$60.05	$60.00
Purchase #3	$8.71	5.593%	$9.1972	$9.20	$9.20	$9.20
Purchase #4	$247.77	13.478%	$281.1644	$281.16	$281.15	$281.20
Purchase #5	$150.75	10.809%	$167.0446	$167.04	$167.05	$167.00
Purchase #6	$11.25	4.543%	$11.7611	$11.76	$11.75	$11.80
Purchase #7	$59.53	12.419%	$66.923	$66.92	$66.90	$66.90
7 purchase totals =	$601.27		$667.5891	$667.58	$667.55	$667.60