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	$189.70	5.832%	$200.7633	$200.76	$200.75	$200.80
Purchase #2	$217.59	11.647%	$242.9327	$242.93	$242.95	$242.90
Purchase #3	$220.64	10.191%	$243.1254	$243.13	$243.15	$243.10
Purchase #4	$71.39	4.123%	$74.3334	$74.33	$74.35	$74.30
Purchase #5	$192.93	6.796%	$206.0415	$206.04	$206.05	$206.00
Purchase #6	$85.62	6.142%	$90.8788	$90.88	$90.90	$90.90
Purchase #7	$22.96	3.767%	$23.8249	$23.82	$23.80	$23.80
7 purchase totals =	$1,000.83		$1,081.9000	$1,081.89	$1,081.95	$1,081.80