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	$97.60	11.686%	$109.0055	$109.01	$109.00	$109.00
Purchase #2	$146.91	5.210%	$154.564	$154.56	$154.55	$154.60
Purchase #3	$175.63	7.689%	$189.1342	$189.13	$189.15	$189.10
Purchase #4	$73.78	5.348%	$77.7258	$77.73	$77.75	$77.70
Purchase #5	$123.61	10.858%	$137.0316	$137.03	$137.05	$137.00
Purchase #6	$216.72	9.767%	$237.887	$237.89	$237.90	$237.90
Purchase #7	$219.54	11.823%	$245.4962	$245.50	$245.50	$245.50
7 purchase totals =	$1,053.79		$1,150.8443	$1,150.85	$1,150.90	$1,150.80