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	$72.46	11.384%	$80.7088	$80.71	$80.70	$80.70
Purchase #2	$141.32	8.799%	$153.7547	$153.75	$153.75	$153.80
Purchase #3	$234.31	3.872%	$243.3825	$243.38	$243.40	$243.40
Purchase #4	$44.67	10.417%	$49.3233	$49.32	$49.30	$49.30
Purchase #5	$88.96	13.475%	$100.9474	$100.95	$100.95	$100.90
Purchase #6	$172.58	13.778%	$196.3581	$196.36	$196.35	$196.40
Purchase #7	$41.98	9.830%	$46.1066	$46.11	$46.10	$46.10
7 purchase totals =	$796.28		$870.5814	$870.58	$870.55	$870.60