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	$171.42	6.560%	$182.6652	$182.67	$182.65	$182.70
Purchase #2	$227.89	6.770%	$243.3182	$243.32	$243.30	$243.30
Purchase #3	$234.96	12.378%	$264.0433	$264.04	$264.05	$264.00
Purchase #4	$247.26	6.538%	$263.4259	$263.43	$263.45	$263.40
Purchase #5	$167.55	7.792%	$180.6055	$180.61	$180.60	$180.60
Purchase #6	$22.54	13.153%	$25.5047	$25.50	$25.50	$25.50
Purchase #7	$234.41	3.244%	$242.0143	$242.01	$242.00	$242.00
7 purchase totals =	$1,306.03		$1,401.5771	$1,401.58	$1,401.55	$1,401.50