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	$171.59	9.769%	$188.3526	$188.35	$188.35	$188.40
Purchase #2	$195.65	9.830%	$214.8824	$214.88	$214.90	$214.90
Purchase #3	$55.57	5.530%	$58.643	$58.64	$58.65	$58.60
Purchase #4	$50.57	8.609%	$54.9236	$54.92	$54.90	$54.90
Purchase #5	$242.62	8.392%	$262.9807	$262.98	$263.00	$263.00
Purchase #6	$143.63	3.333%	$148.4172	$148.42	$148.40	$148.40
Purchase #7	$157.77	9.518%	$172.7865	$172.79	$172.80	$172.80
7 purchase totals =	$1,017.40		$1,100.9860	$1,100.98	$1,101.00	$1,101.00