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	$156.89	9.347%	$171.5545	$171.55	$171.55	$171.60
Purchase #2	$231.40	3.788%	$240.1654	$240.17	$240.15	$240.20
Purchase #3	$204.30	10.214%	$225.1672	$225.17	$225.15	$225.20
Purchase #4	$157.29	5.778%	$166.3782	$166.38	$166.40	$166.40
Purchase #5	$50.94	3.118%	$52.5283	$52.53	$52.55	$52.50
Purchase #6	$29.80	13.178%	$33.727	$33.73	$33.75	$33.70
Purchase #7	$230.48	6.255%	$244.8965	$244.90	$244.90	$244.90
7 purchase totals =	$1,061.10		$1,134.4171	$1,134.43	$1,134.45	$1,134.50