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	$145.77	6.258%	$154.8923	$154.89	$154.90	$154.90
Purchase #2	$10.90	11.760%	$12.1818	$12.18	$12.20	$12.20
Purchase #3	$153.77	9.754%	$168.7687	$168.77	$168.75	$168.80
Purchase #4	$42.77	12.822%	$48.254	$48.25	$48.25	$48.30
Purchase #5	$176.89	6.193%	$187.8448	$187.84	$187.85	$187.80
Purchase #6	$143.47	4.829%	$150.3982	$150.40	$150.40	$150.40
Purchase #7	$235.98	8.592%	$256.2554	$256.26	$256.25	$256.30
7 purchase totals =	$909.55		$978.5952	$978.59	$978.60	$978.70