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	$150.59	5.211%	$158.4372	$158.44	$158.45	$158.40
Purchase #2	$81.92	4.129%	$85.3025	$85.30	$85.30	$85.30
Purchase #3	$68.60	12.538%	$77.2011	$77.20	$77.20	$77.20
Purchase #4	$77.57	5.569%	$81.8899	$81.89	$81.90	$81.90
Purchase #5	$223.33	11.287%	$248.5373	$248.54	$248.55	$248.50
Purchase #6	$106.67	3.429%	$110.3277	$110.33	$110.35	$110.30
Purchase #7	$236.48	9.143%	$258.1014	$258.10	$258.10	$258.10
7 purchase totals =	$945.16		$1,019.7971	$1,019.80	$1,019.85	$1,019.70