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	$145.59	6.549%	$155.1247	$155.12	$155.10	$155.10
Purchase #2	$37.42	4.303%	$39.0302	$39.03	$39.05	$39.00
Purchase #3	$14.53	12.627%	$16.3647	$16.36	$16.35	$16.40
Purchase #4	$45.32	12.793%	$51.1178	$51.12	$51.10	$51.10
Purchase #5	$62.81	13.843%	$71.5048	$71.50	$71.50	$71.50
Purchase #6	$223.61	7.695%	$240.8168	$240.82	$240.80	$240.80
Purchase #7	$146.86	7.814%	$158.3356	$158.34	$158.35	$158.30
7 purchase totals =	$676.14		$732.2946	$732.29	$732.25	$732.20