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	$48.42	5.228%	$50.9514	$50.95	$50.95	$51.00
Purchase #2	$221.67	10.449%	$244.8323	$244.83	$244.85	$244.80
Purchase #3	$126.94	10.474%	$140.2357	$140.24	$140.25	$140.20
Purchase #4	$184.78	10.370%	$203.9417	$203.94	$203.95	$203.90
Purchase #5	$53.63	10.713%	$59.3754	$59.38	$59.40	$59.40
Purchase #6	$231.42	11.542%	$258.1305	$258.13	$258.15	$258.10
Purchase #7	$219.96	8.229%	$238.0605	$238.06	$238.05	$238.10
7 purchase totals =	$1,086.82		$1,195.5275	$1,195.53	$1,195.60	$1,195.50