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	$215.50	10.344%	$237.7913	$237.79	$237.80	$237.80
Purchase #2	$171.38	13.802%	$195.0339	$195.03	$195.05	$195.00
Purchase #3	$91.57	8.188%	$99.0678	$99.07	$99.05	$99.10
Purchase #4	$69.82	4.473%	$72.943	$72.94	$72.95	$72.90
Purchase #5	$116.94	12.145%	$131.1424	$131.14	$131.15	$131.10
Purchase #6	$89.73	12.668%	$101.097	$101.10	$101.10	$101.10
Purchase #7	$122.84	6.158%	$130.4045	$130.40	$130.40	$130.40
7 purchase totals =	$877.78		$967.4799	$967.47	$967.50	$967.40