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	$59.91	6.519%	$63.8155	$63.82	$63.80	$63.80
Purchase #2	$95.38	10.285%	$105.1898	$105.19	$105.20	$105.20
Purchase #3	$242.29	7.282%	$259.9336	$259.93	$259.95	$259.90
Purchase #4	$100.55	10.782%	$111.3913	$111.39	$111.40	$111.40
Purchase #5	$189.75	8.595%	$206.059	$206.06	$206.05	$206.10
Purchase #6	$97.82	4.383%	$102.1075	$102.11	$102.10	$102.10
Purchase #7	$148.74	13.435%	$168.7232	$168.72	$168.70	$168.70
7 purchase totals =	$934.44		$1,017.2199	$1,017.22	$1,017.20	$1,017.20