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	$165.58	8.599%	$179.8182	$179.82	$179.80	$179.80
Purchase #2	$175.70	8.581%	$190.7768	$190.78	$190.80	$190.80
Purchase #3	$7.35	11.696%	$8.2097	$8.21	$8.20	$8.20
Purchase #4	$213.69	8.352%	$231.5374	$231.54	$231.55	$231.50
Purchase #5	$156.85	9.771%	$172.1758	$172.18	$172.20	$172.20
Purchase #6	$195.67	11.693%	$218.5497	$218.55	$218.55	$218.50
Purchase #7	$48.87	11.114%	$54.3014	$54.30	$54.30	$54.30
7 purchase totals =	$963.71		$1,055.3690	$1,055.38	$1,055.40	$1,055.30