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	$168.54	13.363%	$191.062	$191.06	$191.05	$191.10
Purchase #2	$83.78	8.249%	$90.691	$90.69	$90.70	$90.70
Purchase #3	$136.37	13.337%	$154.5577	$154.56	$154.55	$154.60
Purchase #4	$80.60	10.480%	$89.0469	$89.05	$89.05	$89.00
Purchase #5	$98.47	8.405%	$106.7464	$106.75	$106.75	$106.70
Purchase #6	$92.58	3.640%	$95.9499	$95.95	$95.95	$95.90
Purchase #7	$63.39	10.137%	$69.8158	$69.82	$69.80	$69.80
7 purchase totals =	$723.73		$797.8697	$797.88	$797.85	$797.80