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	$91.60	10.829%	$101.5194	$101.52	$101.50	$101.50
Purchase #2	$18.71	9.544%	$20.4957	$20.50	$20.50	$20.50
Purchase #3	$141.42	9.428%	$154.7531	$154.75	$154.75	$154.80
Purchase #4	$246.56	6.631%	$262.9094	$262.91	$262.90	$262.90
Purchase #5	$67.93	9.340%	$74.2747	$74.27	$74.25	$74.30
Purchase #6	$178.57	5.790%	$188.9092	$188.91	$188.90	$188.90
Purchase #7	$139.59	9.817%	$153.2936	$153.29	$153.30	$153.30
7 purchase totals =	$884.38		$956.1551	$956.15	$956.10	$956.20