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	$151.78	7.588%	$163.2971	$163.30	$163.30	$163.30
Purchase #2	$93.69	13.106%	$105.969	$105.97	$105.95	$106.00
Purchase #3	$233.54	7.195%	$250.3432	$250.34	$250.35	$250.30
Purchase #4	$127.31	10.455%	$140.6203	$140.62	$140.60	$140.60
Purchase #5	$218.33	12.449%	$245.5099	$245.51	$245.50	$245.50
Purchase #6	$33.34	4.697%	$34.906	$34.91	$34.90	$34.90
Purchase #7	$57.80	8.654%	$62.802	$62.80	$62.80	$62.80
7 purchase totals =	$915.79		$1,003.4475	$1,003.45	$1,003.40	$1,003.40