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	$79.59	5.422%	$83.9054	$83.91	$83.90	$83.90
Purchase #2	$133.29	6.854%	$142.4257	$142.43	$142.45	$142.40
Purchase #3	$91.94	13.134%	$104.0154	$104.02	$104.00	$104.00
Purchase #4	$212.46	8.118%	$229.7075	$229.71	$229.70	$229.70
Purchase #5	$223.57	8.735%	$243.0988	$243.10	$243.10	$243.10
Purchase #6	$33.65	11.617%	$37.5591	$37.56	$37.55	$37.60
Purchase #7	$205.28	4.163%	$213.8258	$213.83	$213.85	$213.80
7 purchase totals =	$979.78		$1,054.5377	$1,054.56	$1,054.55	$1,054.50