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	$132.98	6.608%	$141.7673	$141.77	$141.75	$141.80
Purchase #2	$211.38	10.431%	$233.429	$233.43	$233.45	$233.40
Purchase #3	$133.73	5.338%	$140.8685	$140.87	$140.85	$140.90
Purchase #4	$141.51	6.296%	$150.4195	$150.42	$150.40	$150.40
Purchase #5	$171.26	7.740%	$184.5155	$184.52	$184.50	$184.50
Purchase #6	$226.37	6.503%	$241.0908	$241.09	$241.10	$241.10
Purchase #7	$173.80	5.539%	$183.4268	$183.43	$183.45	$183.40
7 purchase totals =	$1,191.03		$1,275.5174	$1,275.53	$1,275.50	$1,275.50