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	$109.94	6.180%	$116.7343	$116.73	$116.75	$116.70
Purchase #2	$62.88	3.217%	$64.9028	$64.90	$64.90	$64.90
Purchase #3	$76.96	10.665%	$85.1678	$85.17	$85.15	$85.20
Purchase #4	$192.30	11.640%	$214.6837	$214.68	$214.70	$214.70
Purchase #5	$226.59	8.809%	$246.5503	$246.55	$246.55	$246.60
Purchase #6	$16.61	10.709%	$18.3888	$18.39	$18.40	$18.40
Purchase #7	$136.31	11.384%	$151.8275	$151.83	$151.85	$151.80
7 purchase totals =	$821.59		$898.2552	$898.25	$898.30	$898.30