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	$82.47	3.584%	$85.4257	$85.43	$85.45	$85.40
Purchase #2	$168.40	9.575%	$184.5243	$184.52	$184.50	$184.50
Purchase #3	$48.47	10.256%	$53.4411	$53.44	$53.45	$53.40
Purchase #4	$240.50	11.152%	$267.3206	$267.32	$267.30	$267.30
Purchase #5	$140.61	5.135%	$147.8303	$147.83	$147.85	$147.80
Purchase #6	$71.94	10.114%	$79.216	$79.22	$79.20	$79.20
Purchase #7	$95.64	13.212%	$108.276	$108.28	$108.30	$108.30
7 purchase totals =	$848.03		$926.0340	$926.04	$926.05	$925.90