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	$35.92	4.690%	$37.6046	$37.60	$37.60	$37.60
Purchase #2	$130.62	7.619%	$140.5719	$140.57	$140.55	$140.60
Purchase #3	$190.66	13.669%	$216.7213	$216.72	$216.70	$216.70
Purchase #4	$186.33	9.387%	$203.8208	$203.82	$203.80	$203.80
Purchase #5	$79.30	7.514%	$85.2586	$85.26	$85.25	$85.30
Purchase #6	$56.54	5.119%	$59.4343	$59.43	$59.45	$59.40
Purchase #7	$241.79	9.819%	$265.5314	$265.53	$265.55	$265.50
7 purchase totals =	$921.16		$1,008.9429	$1,008.93	$1,008.90	$1,008.90