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	$47.27	9.532%	$51.7758	$51.78	$51.80	$51.80
Purchase #2	$40.38	6.344%	$42.9417	$42.94	$42.95	$42.90
Purchase #3	$54.95	13.491%	$62.3633	$62.36	$62.35	$62.40
Purchase #4	$152.55	9.855%	$167.5838	$167.58	$167.60	$167.60
Purchase #5	$98.77	7.338%	$106.0177	$106.02	$106.00	$106.00
Purchase #6	$5.86	5.198%	$6.1646	$6.16	$6.15	$6.20
Purchase #7	$61.54	7.165%	$65.9493	$65.95	$65.95	$65.90
7 purchase totals =	$461.32		$502.7962	$502.79	$502.80	$502.80