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	$165.39	7.164%	$177.2385	$177.24	$177.25	$177.20
Purchase #2	$82.87	9.319%	$90.5927	$90.59	$90.60	$90.60
Purchase #3	$208.89	11.569%	$233.0565	$233.06	$233.05	$233.10
Purchase #4	$37.93	4.233%	$39.5356	$39.54	$39.55	$39.50
Purchase #5	$150.57	8.466%	$163.3173	$163.32	$163.30	$163.30
Purchase #6	$73.41	11.332%	$81.7288	$81.73	$81.75	$81.70
Purchase #7	$212.59	9.676%	$233.1602	$233.16	$233.15	$233.20
7 purchase totals =	$931.65		$1,018.6296	$1,018.64	$1,018.65	$1,018.60