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	$30.32	7.801%	$32.6853	$32.69	$32.70	$32.70
Purchase #2	$53.42	12.197%	$59.9356	$59.94	$59.95	$59.90
Purchase #3	$179.49	4.399%	$187.3858	$187.39	$187.40	$187.40
Purchase #4	$161.51	8.846%	$175.7972	$175.80	$175.80	$175.80
Purchase #5	$184.39	11.411%	$205.4307	$205.43	$205.45	$205.40
Purchase #6	$31.27	12.434%	$35.1581	$35.16	$35.15	$35.20
Purchase #7	$211.60	6.246%	$224.8165	$224.82	$224.80	$224.80
7 purchase totals =	$852.00		$921.2092	$921.23	$921.25	$921.20