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	$34.88	8.343%	$37.79	$37.79	$37.80	$37.80
Purchase #2	$241.91	13.432%	$274.4034	$274.40	$274.40	$274.40
Purchase #3	$225.77	8.319%	$244.5518	$244.55	$244.55	$244.60
Purchase #4	$92.71	8.839%	$100.9046	$100.90	$100.90	$100.90
Purchase #5	$85.94	10.214%	$94.7179	$94.72	$94.70	$94.70
Purchase #6	$38.68	9.123%	$42.2088	$42.21	$42.20	$42.20
Purchase #7	$204.60	11.794%	$228.7305	$228.73	$228.75	$228.70
7 purchase totals =	$924.49		$1,023.3070	$1,023.30	$1,023.30	$1,023.30