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	$213.52	11.699%	$238.4997	$238.50	$238.50	$238.50
Purchase #2	$85.46	13.143%	$96.692	$96.69	$96.70	$96.70
Purchase #3	$113.88	8.500%	$123.5598	$123.56	$123.55	$123.60
Purchase #4	$213.35	12.387%	$239.7777	$239.78	$239.80	$239.80
Purchase #5	$242.95	9.360%	$265.6901	$265.69	$265.70	$265.70
Purchase #6	$105.95	6.589%	$112.931	$112.93	$112.95	$112.90
Purchase #7	$141.41	7.615%	$152.1784	$152.18	$152.20	$152.20
7 purchase totals =	$1,116.52		$1,229.3287	$1,229.33	$1,229.40	$1,229.40