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	$186.34	3.111%	$192.137	$192.14	$192.15	$192.10
Purchase #2	$69.86	10.582%	$77.2526	$77.25	$77.25	$77.30
Purchase #3	$72.80	8.420%	$78.9298	$78.93	$78.95	$78.90
Purchase #4	$53.40	4.521%	$55.8142	$55.81	$55.80	$55.80
Purchase #5	$59.89	4.635%	$62.6659	$62.67	$62.65	$62.70
Purchase #6	$96.39	12.517%	$108.4551	$108.46	$108.45	$108.50
Purchase #7	$77.25	7.400%	$82.9665	$82.97	$82.95	$83.00
7 purchase totals =	$615.93		$658.2211	$658.23	$658.20	$658.30