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	$246.45	7.503%	$264.9411	$264.94	$264.95	$264.90
Purchase #2	$133.35	9.627%	$146.1876	$146.19	$146.20	$146.20
Purchase #3	$59.73	10.352%	$65.9132	$65.91	$65.90	$65.90
Purchase #4	$186.62	4.760%	$195.5031	$195.50	$195.50	$195.50
Purchase #5	$59.98	12.706%	$67.6011	$67.60	$67.60	$67.60
Purchase #6	$58.71	5.215%	$61.7717	$61.77	$61.75	$61.80
Purchase #7	$11.44	8.250%	$12.3838	$12.38	$12.40	$12.40
7 purchase totals =	$756.28		$814.3016	$814.29	$814.30	$814.30