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	$69.65	7.125%	$74.6126	$74.61	$74.60	$74.60
Purchase #2	$139.54	5.690%	$147.4798	$147.48	$147.50	$147.50
Purchase #3	$57.34	9.251%	$62.6445	$62.64	$62.65	$62.60
Purchase #4	$29.96	8.623%	$32.5435	$32.54	$32.55	$32.50
Purchase #5	$146.90	3.170%	$151.5567	$151.56	$151.55	$151.60
Purchase #6	$76.39	5.642%	$80.6999	$80.70	$80.70	$80.70
Purchase #7	$243.49	5.490%	$256.8576	$256.86	$256.85	$256.90
7 purchase totals =	$763.27		$806.3946	$806.39	$806.40	$806.40