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	$96.71	13.217%	$109.4922	$109.49	$109.50	$109.50
Purchase #2	$97.29	8.768%	$105.8204	$105.82	$105.80	$105.80
Purchase #3	$51.60	3.596%	$53.4555	$53.46	$53.45	$53.50
Purchase #4	$153.38	12.593%	$172.6951	$172.70	$172.70	$172.70
Purchase #5	$119.73	3.776%	$124.251	$124.25	$124.25	$124.30
Purchase #6	$157.85	10.810%	$174.9136	$174.91	$174.90	$174.90
Purchase #7	$213.64	6.435%	$227.3877	$227.39	$227.40	$227.40
7 purchase totals =	$890.20		$968.0155	$968.02	$968.00	$968.10