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	$156.93	10.203%	$172.9416	$172.94	$172.95	$172.90
Purchase #2	$170.29	11.735%	$190.2735	$190.27	$190.25	$190.30
Purchase #3	$7.45	5.570%	$7.865	$7.87	$7.85	$7.90
Purchase #4	$155.60	6.762%	$166.1217	$166.12	$166.10	$166.10
Purchase #5	$194.36	13.692%	$220.9718	$220.97	$220.95	$221.00
Purchase #6	$41.55	8.590%	$45.1191	$45.12	$45.10	$45.10
Purchase #7	$115.67	10.757%	$128.1126	$128.11	$128.10	$128.10
7 purchase totals =	$841.85		$931.4053	$931.40	$931.30	$931.40