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	$102.88	9.511%	$112.6649	$112.66	$112.65	$112.70
Purchase #2	$95.55	4.111%	$99.4781	$99.48	$99.50	$99.50
Purchase #3	$206.38	11.142%	$229.3749	$229.37	$229.35	$229.40
Purchase #4	$57.28	6.400%	$60.9459	$60.95	$60.95	$60.90
Purchase #5	$177.27	11.459%	$197.5834	$197.58	$197.60	$197.60
Purchase #6	$50.65	3.139%	$52.2399	$52.24	$52.25	$52.20
Purchase #7	$190.54	3.131%	$196.5058	$196.51	$196.50	$196.50
7 purchase totals =	$880.55		$948.7929	$948.79	$948.80	$948.80