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	$82.70	8.518%	$89.7444	$89.74	$89.75	$89.70
Purchase #2	$231.69	8.205%	$250.7002	$250.70	$250.70	$250.70
Purchase #3	$177.53	6.704%	$189.4316	$189.43	$189.45	$189.40
Purchase #4	$109.47	7.587%	$117.7755	$117.78	$117.80	$117.80
Purchase #5	$50.44	11.435%	$56.2078	$56.21	$56.20	$56.20
Purchase #6	$141.72	10.707%	$156.894	$156.89	$156.90	$156.90
Purchase #7	$144.87	5.186%	$152.383	$152.38	$152.40	$152.40
7 purchase totals =	$938.42		$1,013.1365	$1,013.13	$1,013.20	$1,013.10