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	$115.87	12.750%	$130.6434	$130.64	$130.65	$130.60
Purchase #2	$183.59	11.303%	$204.3412	$204.34	$204.35	$204.30
Purchase #3	$195.38	8.446%	$211.8818	$211.88	$211.90	$211.90
Purchase #4	$7.83	4.291%	$8.166	$8.17	$8.15	$8.20
Purchase #5	$100.28	3.265%	$103.5541	$103.55	$103.55	$103.60
Purchase #6	$40.67	11.834%	$45.4829	$45.48	$45.50	$45.50
Purchase #7	$73.44	12.676%	$82.7493	$82.75	$82.75	$82.70
7 purchase totals =	$717.06		$786.8187	$786.81	$786.85	$786.80