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	$134.50	13.501%	$152.6588	$152.66	$152.65	$152.70
Purchase #2	$60.88	4.454%	$63.5916	$63.59	$63.60	$63.60
Purchase #3	$104.72	10.363%	$115.5721	$115.57	$115.55	$115.60
Purchase #4	$162.60	11.562%	$181.3998	$181.40	$181.40	$181.40
Purchase #5	$109.32	4.813%	$114.5816	$114.58	$114.60	$114.60
Purchase #6	$35.91	13.143%	$40.6297	$40.63	$40.65	$40.60
Purchase #7	$216.51	5.538%	$228.5003	$228.50	$228.50	$228.50
7 purchase totals =	$824.44		$896.9339	$896.93	$896.95	$897.00