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	$21.30	5.555%	$22.4832	$22.48	$22.50	$22.50
Purchase #2	$83.46	7.475%	$89.6986	$89.70	$89.70	$89.70
Purchase #3	$100.85	12.813%	$113.7719	$113.77	$113.75	$113.80
Purchase #4	$143.60	7.507%	$154.3801	$154.38	$154.40	$154.40
Purchase #5	$176.51	6.620%	$188.195	$188.20	$188.20	$188.20
Purchase #6	$199.55	5.151%	$209.8288	$209.83	$209.85	$209.80
Purchase #7	$217.46	12.625%	$244.9143	$244.91	$244.90	$244.90
7 purchase totals =	$942.73		$1,023.2719	$1,023.27	$1,023.30	$1,023.30