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	$32.70	4.477%	$34.164	$34.16	$34.15	$34.20
Purchase #2	$34.94	6.233%	$37.1178	$37.12	$37.10	$37.10
Purchase #3	$169.96	12.805%	$191.7234	$191.72	$191.70	$191.70
Purchase #4	$162.62	13.713%	$184.9201	$184.92	$184.90	$184.90
Purchase #5	$177.60	12.127%	$199.1376	$199.14	$199.15	$199.10
Purchase #6	$94.40	12.115%	$105.8366	$105.84	$105.85	$105.80
Purchase #7	$84.43	13.119%	$95.5064	$95.51	$95.50	$95.50
7 purchase totals =	$756.65		$848.4059	$848.41	$848.35	$848.30