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	$178.89	5.132%	$188.0706	$188.07	$188.05	$188.10
Purchase #2	$94.73	9.283%	$103.5238	$103.52	$103.50	$103.50
Purchase #3	$27.78	7.344%	$29.8202	$29.82	$29.80	$29.80
Purchase #4	$147.51	5.157%	$155.1171	$155.12	$155.10	$155.10
Purchase #5	$199.25	11.646%	$222.4547	$222.45	$222.45	$222.50
Purchase #6	$246.82	7.229%	$264.6626	$264.66	$264.65	$264.70
Purchase #7	$93.46	13.266%	$105.8584	$105.86	$105.85	$105.90
7 purchase totals =	$988.44		$1,069.5074	$1,069.50	$1,069.40	$1,069.60