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	$153.33	9.472%	$167.8534	$167.85	$167.85	$167.90
Purchase #2	$72.34	4.723%	$75.7566	$75.76	$75.75	$75.80
Purchase #3	$41.85	5.672%	$44.2237	$44.22	$44.20	$44.20
Purchase #4	$196.81	9.769%	$216.0364	$216.04	$216.05	$216.00
Purchase #5	$221.66	10.764%	$245.5195	$245.52	$245.50	$245.50
Purchase #6	$230.83	6.533%	$245.9101	$245.91	$245.90	$245.90
Purchase #7	$6.66	13.216%	$7.5402	$7.54	$7.55	$7.50
7 purchase totals =	$923.48		$1,002.8399	$1,002.84	$1,002.80	$1,002.80