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	$216.49	8.250%	$234.3504	$234.35	$234.35	$234.40
Purchase #2	$152.46	6.553%	$162.4507	$162.45	$162.45	$162.50
Purchase #3	$197.72	9.427%	$216.3591	$216.36	$216.35	$216.40
Purchase #4	$44.55	8.119%	$48.167	$48.17	$48.15	$48.20
Purchase #5	$203.85	10.333%	$224.9138	$224.91	$224.90	$224.90
Purchase #6	$120.25	13.814%	$136.8613	$136.86	$136.85	$136.90
Purchase #7	$36.38	6.821%	$38.8615	$38.86	$38.85	$38.90
7 purchase totals =	$971.70		$1,061.9638	$1,061.96	$1,061.90	$1,062.20