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	$40.42	3.283%	$41.747	$41.75	$41.75	$41.70
Purchase #2	$232.59	3.384%	$240.4608	$240.46	$240.45	$240.50
Purchase #3	$173.45	10.535%	$191.723	$191.72	$191.70	$191.70
Purchase #4	$146.30	10.645%	$161.8736	$161.87	$161.85	$161.90
Purchase #5	$190.28	3.168%	$196.3081	$196.31	$196.30	$196.30
Purchase #6	$31.83	13.804%	$36.2238	$36.22	$36.20	$36.20
Purchase #7	$116.73	6.167%	$123.9287	$123.93	$123.95	$123.90
7 purchase totals =	$931.60		$992.2650	$992.26	$992.20	$992.20