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	$186.85	13.226%	$211.5628	$211.56	$211.55	$211.60
Purchase #2	$6.91	5.351%	$7.2798	$7.28	$7.30	$7.30
Purchase #3	$6.82	9.222%	$7.4489	$7.45	$7.45	$7.40
Purchase #4	$164.36	9.229%	$179.5288	$179.53	$179.55	$179.50
Purchase #5	$93.75	7.624%	$100.8975	$100.90	$100.90	$100.90
Purchase #6	$205.73	10.590%	$227.5168	$227.52	$227.50	$227.50
Purchase #7	$82.46	6.684%	$87.9716	$87.97	$87.95	$88.00
7 purchase totals =	$746.88		$822.2062	$822.21	$822.20	$822.20