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	$172.63	7.565%	$185.6895	$185.69	$185.70	$185.70
Purchase #2	$91.88	10.185%	$101.238	$101.24	$101.25	$101.20
Purchase #3	$235.38	6.540%	$250.7739	$250.77	$250.75	$250.80
Purchase #4	$166.25	11.452%	$185.289	$185.29	$185.30	$185.30
Purchase #5	$225.96	10.810%	$250.3863	$250.39	$250.40	$250.40
Purchase #6	$148.62	5.508%	$156.806	$156.81	$156.80	$156.80
Purchase #7	$247.91	3.583%	$256.7926	$256.79	$256.80	$256.80
7 purchase totals =	$1,288.63		$1,386.9753	$1,386.98	$1,387.00	$1,387.00