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	$76.73	9.290%	$83.8582	$83.86	$83.85	$83.90
Purchase #2	$60.93	8.250%	$65.9567	$65.96	$65.95	$66.00
Purchase #3	$99.71	9.462%	$109.1446	$109.14	$109.15	$109.10
Purchase #4	$158.68	8.114%	$171.5553	$171.56	$171.55	$171.60
Purchase #5	$150.75	3.248%	$155.6464	$155.65	$155.65	$155.60
Purchase #6	$192.89	13.427%	$218.7893	$218.79	$218.80	$218.80
Purchase #7	$77.98	5.581%	$82.3321	$82.33	$82.35	$82.30
7 purchase totals =	$817.67		$887.2826	$887.29	$887.30	$887.30