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	$103.34	6.782%	$110.3485	$110.35	$110.35	$110.30
Purchase #2	$29.43	6.172%	$31.2464	$31.25	$31.25	$31.20
Purchase #3	$144.63	7.492%	$155.4657	$155.47	$155.45	$155.50
Purchase #4	$68.61	5.372%	$72.2957	$72.30	$72.30	$72.30
Purchase #5	$72.91	5.476%	$76.9026	$76.90	$76.90	$76.90
Purchase #6	$215.46	7.413%	$231.432	$231.43	$231.45	$231.40
Purchase #7	$56.41	7.266%	$60.5088	$60.51	$60.50	$60.50
7 purchase totals =	$690.79		$738.1997	$738.21	$738.20	$738.10