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	$146.79	8.801%	$159.709	$159.71	$159.70	$159.70
Purchase #2	$49.61	11.261%	$55.1966	$55.20	$55.20	$55.20
Purchase #3	$209.39	6.858%	$223.75	$223.75	$223.75	$223.80
Purchase #4	$247.72	6.381%	$263.527	$263.53	$263.55	$263.50
Purchase #5	$81.51	4.837%	$85.4526	$85.45	$85.45	$85.50
Purchase #6	$178.87	6.340%	$190.2104	$190.21	$190.20	$190.20
Purchase #7	$22.46	7.524%	$24.1499	$24.15	$24.15	$24.10
7 purchase totals =	$936.35		$1,001.9955	$1,002.00	$1,002.00	$1,002.00