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	$131.76	7.402%	$141.5129	$141.51	$141.50	$141.50
Purchase #2	$29.50	8.644%	$32.05	$32.05	$32.05	$32.10
Purchase #3	$136.26	5.109%	$143.2215	$143.22	$143.20	$143.20
Purchase #4	$162.47	11.551%	$181.2369	$181.24	$181.25	$181.20
Purchase #5	$6.61	13.656%	$7.5127	$7.51	$7.50	$7.50
Purchase #6	$246.78	9.674%	$270.6535	$270.65	$270.65	$270.70
Purchase #7	$167.79	13.313%	$190.1279	$190.13	$190.15	$190.10
7 purchase totals =	$881.17		$966.3154	$966.31	$966.30	$966.30