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	$48.84	3.816%	$50.7037	$50.70	$50.70	$50.70
Purchase #2	$56.79	11.639%	$63.3998	$63.40	$63.40	$63.40
Purchase #3	$119.58	9.845%	$131.3527	$131.35	$131.35	$131.40
Purchase #4	$237.89	6.548%	$253.467	$253.47	$253.45	$253.50
Purchase #5	$243.50	13.113%	$275.4302	$275.43	$275.45	$275.40
Purchase #6	$145.72	3.292%	$150.5171	$150.52	$150.50	$150.50
Purchase #7	$51.32	9.689%	$56.2924	$56.29	$56.30	$56.30
7 purchase totals =	$903.64		$981.1629	$981.16	$981.15	$981.20