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	$195.79	9.850%	$215.0753	$215.08	$215.10	$215.10
Purchase #2	$33.96	11.864%	$37.989	$37.99	$38.00	$38.00
Purchase #3	$246.76	11.406%	$274.9054	$274.91	$274.90	$274.90
Purchase #4	$37.49	11.803%	$41.9149	$41.91	$41.90	$41.90
Purchase #5	$37.34	12.606%	$42.0471	$42.05	$42.05	$42.00
Purchase #6	$171.48	10.519%	$189.518	$189.52	$189.50	$189.50
Purchase #7	$89.89	12.538%	$101.1604	$101.16	$101.15	$101.20
7 purchase totals =	$812.71		$902.6101	$902.62	$902.60	$902.60