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	$150.66	11.540%	$168.0462	$168.05	$168.05	$168.00
Purchase #2	$104.64	4.761%	$109.6219	$109.62	$109.60	$109.60
Purchase #3	$101.73	6.594%	$108.4381	$108.44	$108.45	$108.40
Purchase #4	$163.83	13.459%	$185.8799	$185.88	$185.90	$185.90
Purchase #5	$216.74	5.438%	$228.5263	$228.53	$228.55	$228.50
Purchase #6	$244.46	6.325%	$259.9221	$259.92	$259.90	$259.90
Purchase #7	$212.52	7.433%	$228.3166	$228.32	$228.30	$228.30
7 purchase totals =	$1,194.58		$1,288.7511	$1,288.76	$1,288.75	$1,288.60