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	$159.64	7.220%	$171.166	$171.17	$171.15	$171.20
Purchase #2	$201.97	10.417%	$223.0092	$223.01	$223.00	$223.00
Purchase #3	$130.52	10.563%	$144.3068	$144.31	$144.30	$144.30
Purchase #4	$41.77	11.353%	$46.5121	$46.51	$46.50	$46.50
Purchase #5	$164.48	8.452%	$178.3818	$178.38	$178.40	$178.40
Purchase #6	$108.89	9.411%	$119.1376	$119.14	$119.15	$119.10
Purchase #7	$55.61	6.212%	$59.0645	$59.06	$59.05	$59.10
7 purchase totals =	$862.88		$941.5780	$941.58	$941.55	$941.60