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	$131.68	4.284%	$137.3212	$137.32	$137.30	$137.30
Purchase #2	$124.51	3.155%	$128.4383	$128.44	$128.45	$128.40
Purchase #3	$72.60	8.705%	$78.9198	$78.92	$78.90	$78.90
Purchase #4	$39.79	11.156%	$44.229	$44.23	$44.25	$44.20
Purchase #5	$177.41	9.648%	$194.5265	$194.53	$194.55	$194.50
Purchase #6	$21.73	4.435%	$22.6937	$22.69	$22.70	$22.70
Purchase #7	$148.87	5.166%	$156.5606	$156.56	$156.55	$156.60
7 purchase totals =	$716.59		$762.6891	$762.69	$762.70	$762.60