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	$148.80	7.623%	$160.143	$160.14	$160.15	$160.10
Purchase #2	$185.49	12.659%	$208.9712	$208.97	$208.95	$209.00
Purchase #3	$220.82	7.250%	$236.8295	$236.83	$236.85	$236.80
Purchase #4	$80.87	11.302%	$90.0099	$90.01	$90.00	$90.00
Purchase #5	$234.27	7.113%	$250.9336	$250.93	$250.95	$250.90
Purchase #6	$127.86	7.439%	$137.3715	$137.37	$137.35	$137.40
Purchase #7	$146.79	12.114%	$164.5721	$164.57	$164.55	$164.60
7 purchase totals =	$1,144.90		$1,248.8308	$1,248.82	$1,248.80	$1,248.80