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	$85.65	12.244%	$96.137	$96.14	$96.15	$96.10
Purchase #2	$230.59	3.582%	$238.8497	$238.85	$238.85	$238.80
Purchase #3	$246.79	9.606%	$270.4966	$270.50	$270.50	$270.50
Purchase #4	$200.55	13.533%	$227.6904	$227.69	$227.70	$227.70
Purchase #5	$128.42	10.272%	$141.6113	$141.61	$141.60	$141.60
Purchase #6	$103.30	11.230%	$114.9006	$114.90	$114.90	$114.90
Purchase #7	$40.61	12.144%	$45.5417	$45.54	$45.55	$45.50
7 purchase totals =	$1,035.91		$1,135.2273	$1,135.23	$1,135.25	$1,135.10