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	$116.90	5.275%	$123.0665	$123.07	$123.05	$123.10
Purchase #2	$240.61	5.470%	$253.7714	$253.77	$253.75	$253.80
Purchase #3	$55.60	11.228%	$61.8428	$61.84	$61.85	$61.80
Purchase #4	$217.55	11.559%	$242.6966	$242.70	$242.70	$242.70
Purchase #5	$140.82	9.598%	$154.3359	$154.34	$154.35	$154.30
Purchase #6	$223.77	6.589%	$238.5142	$238.51	$238.50	$238.50
Purchase #7	$150.36	7.756%	$162.0219	$162.02	$162.00	$162.00
7 purchase totals =	$1,145.61		$1,236.2493	$1,236.25	$1,236.20	$1,236.20