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	$198.34	11.820%	$221.7838	$221.78	$221.80	$221.80
Purchase #2	$88.44	13.632%	$100.4961	$100.50	$100.50	$100.50
Purchase #3	$189.60	3.448%	$196.1374	$196.14	$196.15	$196.10
Purchase #4	$42.26	3.486%	$43.7332	$43.73	$43.75	$43.70
Purchase #5	$88.35	3.339%	$91.3	$91.30	$91.30	$91.30
Purchase #6	$26.73	7.774%	$28.808	$28.81	$28.80	$28.80
Purchase #7	$18.38	11.769%	$20.5431	$20.54	$20.55	$20.50
7 purchase totals =	$652.10		$702.8016	$702.80	$702.85	$702.70