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	$196.70	9.392%	$215.1741	$215.17	$215.15	$215.20
Purchase #2	$89.80	13.459%	$101.8862	$101.89	$101.90	$101.90
Purchase #3	$150.53	5.706%	$159.1192	$159.12	$159.10	$159.10
Purchase #4	$225.89	12.148%	$253.3311	$253.33	$253.35	$253.30
Purchase #5	$74.75	13.538%	$84.8697	$84.87	$84.85	$84.90
Purchase #6	$125.94	4.479%	$131.5809	$131.58	$131.60	$131.60
Purchase #7	$45.82	5.700%	$48.4317	$48.43	$48.45	$48.40
7 purchase totals =	$909.43		$994.3929	$994.39	$994.40	$994.40