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	$132.25	8.790%	$143.8748	$143.87	$143.85	$143.90
Purchase #2	$170.60	10.648%	$188.7655	$188.77	$188.75	$188.80
Purchase #3	$71.62	11.338%	$79.7403	$79.74	$79.75	$79.70
Purchase #4	$49.88	7.470%	$53.606	$53.61	$53.60	$53.60
Purchase #5	$13.33	4.119%	$13.8791	$13.88	$13.90	$13.90
Purchase #6	$47.95	13.651%	$54.4957	$54.50	$54.50	$54.50
Purchase #7	$157.73	11.288%	$175.5346	$175.53	$175.55	$175.50
7 purchase totals =	$643.36		$709.8960	$709.90	$709.90	$709.90