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	$141.43	6.227%	$150.2368	$150.24	$150.25	$150.20
Purchase #2	$188.81	3.822%	$196.0263	$196.03	$196.05	$196.00
Purchase #3	$209.53	10.394%	$231.3085	$231.31	$231.30	$231.30
Purchase #4	$232.91	6.390%	$247.7929	$247.79	$247.80	$247.80
Purchase #5	$196.28	13.233%	$222.2537	$222.25	$222.25	$222.30
Purchase #6	$207.80	3.678%	$215.4429	$215.44	$215.45	$215.40
Purchase #7	$141.96	8.208%	$153.6121	$153.61	$153.60	$153.60
7 purchase totals =	$1,318.72		$1,416.6732	$1,416.67	$1,416.70	$1,416.60