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	$72.41	4.736%	$75.8393	$75.84	$75.85	$75.80
Purchase #2	$25.53	9.495%	$27.9541	$27.95	$27.95	$28.00
Purchase #3	$98.77	6.618%	$105.3066	$105.31	$105.30	$105.30
Purchase #4	$59.35	3.622%	$61.4997	$61.50	$61.50	$61.50
Purchase #5	$137.25	5.279%	$144.4954	$144.50	$144.50	$144.50
Purchase #6	$135.50	13.433%	$153.7017	$153.70	$153.70	$153.70
Purchase #7	$156.92	7.610%	$168.8616	$168.86	$168.85	$168.90
7 purchase totals =	$685.73		$737.6584	$737.66	$737.65	$737.70