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	$35.87	5.731%	$37.9257	$37.93	$37.95	$37.90
Purchase #2	$229.32	8.701%	$249.2731	$249.27	$249.25	$249.30
Purchase #3	$108.30	7.727%	$116.6683	$116.67	$116.65	$116.70
Purchase #4	$190.50	11.221%	$211.876	$211.88	$211.90	$211.90
Purchase #5	$74.38	12.272%	$83.5079	$83.51	$83.50	$83.50
Purchase #6	$98.84	4.581%	$103.3679	$103.37	$103.35	$103.40
Purchase #7	$205.53	12.444%	$231.1062	$231.11	$231.10	$231.10
7 purchase totals =	$942.74		$1,033.7251	$1,033.74	$1,033.70	$1,033.80