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	$131.46	4.760%	$137.7175	$137.72	$137.70	$137.70
Purchase #2	$66.33	7.598%	$71.3698	$71.37	$71.35	$71.40
Purchase #3	$185.67	10.768%	$205.6629	$205.66	$205.65	$205.70
Purchase #4	$66.30	9.180%	$72.3863	$72.39	$72.40	$72.40
Purchase #5	$197.96	11.779%	$221.2777	$221.28	$221.30	$221.30
Purchase #6	$244.56	6.271%	$259.8964	$259.90	$259.90	$259.90
Purchase #7	$80.51	4.314%	$83.9832	$83.98	$84.00	$84.00
7 purchase totals =	$972.79		$1,052.2938	$1,052.30	$1,052.30	$1,052.40