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	$74.77	9.761%	$82.0683	$82.07	$82.05	$82.10
Purchase #2	$144.27	10.556%	$159.4991	$159.50	$159.50	$159.50
Purchase #3	$239.27	10.465%	$264.3096	$264.31	$264.30	$264.30
Purchase #4	$151.41	10.684%	$167.5866	$167.59	$167.60	$167.60
Purchase #5	$64.92	8.207%	$70.248	$70.25	$70.25	$70.20
Purchase #6	$52.35	10.499%	$57.8462	$57.85	$57.85	$57.80
Purchase #7	$183.81	9.171%	$200.6672	$200.67	$200.65	$200.70
7 purchase totals =	$910.80		$1,002.2250	$1,002.24	$1,002.20	$1,002.20