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	$88.86	3.341%	$91.8288	$91.83	$91.85	$91.80
Purchase #2	$220.99	10.421%	$244.0194	$244.02	$244.00	$244.00
Purchase #3	$201.98	6.113%	$214.327	$214.33	$214.35	$214.30
Purchase #4	$216.42	5.235%	$227.7496	$227.75	$227.75	$227.70
Purchase #5	$68.81	10.824%	$76.258	$76.26	$76.25	$76.30
Purchase #6	$90.61	10.150%	$99.8069	$99.81	$99.80	$99.80
Purchase #7	$52.64	4.158%	$54.8288	$54.83	$54.85	$54.80
7 purchase totals =	$940.31		$1,008.8185	$1,008.83	$1,008.85	$1,008.70