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	$83.28	10.822%	$92.2926	$92.29	$92.30	$92.30
Purchase #2	$64.77	7.197%	$69.4315	$69.43	$69.45	$69.40
Purchase #3	$75.30	9.289%	$82.2946	$82.29	$82.30	$82.30
Purchase #4	$33.48	6.690%	$35.7198	$35.72	$35.70	$35.70
Purchase #5	$197.33	12.158%	$221.3214	$221.32	$221.30	$221.30
Purchase #6	$14.59	8.615%	$15.8469	$15.85	$15.85	$15.80
Purchase #7	$49.41	11.594%	$55.1386	$55.14	$55.15	$55.10
7 purchase totals =	$518.16		$572.0454	$572.04	$572.05	$571.90