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	$155.33	8.218%	$168.095	$168.10	$168.10	$168.10
Purchase #2	$159.71	13.184%	$180.7662	$180.77	$180.75	$180.80
Purchase #3	$193.70	9.558%	$212.2138	$212.21	$212.20	$212.20
Purchase #4	$168.69	13.635%	$191.6909	$191.69	$191.70	$191.70
Purchase #5	$131.57	6.833%	$140.5602	$140.56	$140.55	$140.60
Purchase #6	$182.89	12.562%	$205.8646	$205.86	$205.85	$205.90
Purchase #7	$6.33	3.702%	$6.5643	$6.56	$6.55	$6.60
7 purchase totals =	$998.22		$1,105.7550	$1,105.75	$1,105.70	$1,105.90