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	$194.72	3.185%	$200.9218	$200.92	$200.90	$200.90
Purchase #2	$89.99	7.658%	$96.8814	$96.88	$96.90	$96.90
Purchase #3	$46.43	13.460%	$52.6795	$52.68	$52.70	$52.70
Purchase #4	$32.80	6.740%	$35.0107	$35.01	$35.00	$35.00
Purchase #5	$222.48	12.869%	$251.111	$251.11	$251.10	$251.10
Purchase #6	$223.59	7.679%	$240.7595	$240.76	$240.75	$240.80
Purchase #7	$189.58	10.371%	$209.2413	$209.24	$209.25	$209.20
7 purchase totals =	$999.59		$1,086.6052	$1,086.60	$1,086.60	$1,086.60