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	$72.51	11.518%	$80.8617	$80.86	$80.85	$80.90
Purchase #2	$145.30	4.135%	$151.3082	$151.31	$151.30	$151.30
Purchase #3	$29.69	11.153%	$33.0013	$33.00	$33.00	$33.00
Purchase #4	$142.61	5.113%	$149.9016	$149.90	$149.90	$149.90
Purchase #5	$237.79	13.338%	$269.5064	$269.51	$269.50	$269.50
Purchase #6	$135.31	4.651%	$141.6033	$141.60	$141.60	$141.60
Purchase #7	$172.47	13.673%	$196.0518	$196.05	$196.05	$196.10
7 purchase totals =	$935.68		$1,022.2343	$1,022.23	$1,022.20	$1,022.30