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	$86.84	13.690%	$98.7284	$98.73	$98.75	$98.70
Purchase #2	$190.89	11.555%	$212.9473	$212.95	$212.95	$212.90
Purchase #3	$9.72	9.538%	$10.6471	$10.65	$10.65	$10.60
Purchase #4	$179.46	3.344%	$185.4611	$185.46	$185.45	$185.50
Purchase #5	$189.95	5.583%	$200.5549	$200.55	$200.55	$200.60
Purchase #6	$125.27	4.404%	$130.7869	$130.79	$130.80	$130.80
Purchase #7	$228.50	4.277%	$238.2729	$238.27	$238.25	$238.30
7 purchase totals =	$1,010.63		$1,077.3986	$1,077.40	$1,077.40	$1,077.40