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	$176.78	8.324%	$191.4952	$191.50	$191.50	$191.50
Purchase #2	$237.98	4.863%	$249.553	$249.55	$249.55	$249.60
Purchase #3	$137.55	4.553%	$143.8127	$143.81	$143.80	$143.80
Purchase #4	$139.95	9.140%	$152.7414	$152.74	$152.75	$152.70
Purchase #5	$22.80	11.627%	$25.451	$25.45	$25.45	$25.50
Purchase #6	$50.48	3.773%	$52.3846	$52.38	$52.40	$52.40
Purchase #7	$101.66	7.519%	$109.3038	$109.30	$109.30	$109.30
7 purchase totals =	$867.20		$924.7417	$924.73	$924.75	$924.80