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	$65.86	11.611%	$73.507	$73.51	$73.50	$73.50
Purchase #2	$168.30	7.313%	$180.6078	$180.61	$180.60	$180.60
Purchase #3	$145.99	4.182%	$152.0953	$152.10	$152.10	$152.10
Purchase #4	$228.40	8.701%	$248.2731	$248.27	$248.25	$248.30
Purchase #5	$44.57	5.140%	$46.8609	$46.86	$46.85	$46.90
Purchase #6	$124.59	5.782%	$131.7938	$131.79	$131.80	$131.80
Purchase #7	$210.96	8.244%	$228.3515	$228.35	$228.35	$228.40
7 purchase totals =	$988.67		$1,061.4894	$1,061.49	$1,061.45	$1,061.60