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	$183.27	4.457%	$191.4383	$191.44	$191.45	$191.40
Purchase #2	$132.96	4.329%	$138.7158	$138.72	$138.70	$138.70
Purchase #3	$240.74	6.263%	$255.8175	$255.82	$255.80	$255.80
Purchase #4	$173.52	10.331%	$191.4464	$191.45	$191.45	$191.40
Purchase #5	$88.69	13.325%	$100.5079	$100.51	$100.50	$100.50
Purchase #6	$160.58	13.540%	$182.3225	$182.32	$182.30	$182.30
Purchase #7	$7.77	6.615%	$8.284	$8.28	$8.30	$8.30
7 purchase totals =	$987.53		$1,068.5324	$1,068.54	$1,068.50	$1,068.40