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	$52.62	13.524%	$59.7363	$59.74	$59.75	$59.70
Purchase #2	$102.81	5.381%	$108.3422	$108.34	$108.35	$108.30
Purchase #3	$19.67	5.592%	$20.7699	$20.77	$20.75	$20.80
Purchase #4	$133.48	5.541%	$140.8761	$140.88	$140.90	$140.90
Purchase #5	$248.46	4.760%	$260.2867	$260.29	$260.30	$260.30
Purchase #6	$213.47	4.270%	$222.5852	$222.59	$222.60	$222.60
Purchase #7	$123.91	6.500%	$131.9642	$131.96	$131.95	$132.00
7 purchase totals =	$894.42		$944.5606	$944.57	$944.60	$944.60