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	$209.56	3.747%	$217.4122	$217.41	$217.40	$217.40
Purchase #2	$67.43	6.186%	$71.6012	$71.60	$71.60	$71.60
Purchase #3	$174.49	12.741%	$196.7218	$196.72	$196.70	$196.70
Purchase #4	$239.48	10.511%	$264.6517	$264.65	$264.65	$264.70
Purchase #5	$170.87	8.200%	$184.8813	$184.88	$184.90	$184.90
Purchase #6	$224.39	11.780%	$250.8231	$250.82	$250.80	$250.80
Purchase #7	$149.36	6.304%	$158.7757	$158.78	$158.80	$158.80
7 purchase totals =	$1,235.58		$1,344.8670	$1,344.86	$1,344.85	$1,344.90