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	$101.77	9.410%	$111.3466	$111.35	$111.35	$111.30
Purchase #2	$18.98	6.564%	$20.2258	$20.23	$20.25	$20.20
Purchase #3	$101.64	4.454%	$106.167	$106.17	$106.15	$106.20
Purchase #4	$214.36	6.780%	$228.8936	$228.89	$228.90	$228.90
Purchase #5	$147.35	7.727%	$158.7357	$158.74	$158.75	$158.70
Purchase #6	$100.58	7.778%	$108.4031	$108.40	$108.40	$108.40
Purchase #7	$219.26	10.244%	$241.721	$241.72	$241.70	$241.70
7 purchase totals =	$903.94		$975.4928	$975.50	$975.50	$975.40