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	$179.49	11.550%	$200.2211	$200.22	$200.20	$200.20
Purchase #2	$76.90	6.699%	$82.0515	$82.05	$82.05	$82.10
Purchase #3	$192.55	13.501%	$218.5462	$218.55	$218.55	$218.50
Purchase #4	$38.35	11.262%	$42.669	$42.67	$42.65	$42.70
Purchase #5	$153.57	10.219%	$169.2633	$169.26	$169.25	$169.30
Purchase #6	$175.55	10.575%	$194.1144	$194.11	$194.10	$194.10
Purchase #7	$129.79	11.349%	$144.5199	$144.52	$144.50	$144.50
7 purchase totals =	$946.20		$1,051.3854	$1,051.38	$1,051.30	$1,051.40