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	$119.42	9.196%	$130.4019	$130.40	$130.40	$130.40
Purchase #2	$19.61	11.157%	$21.7979	$21.80	$21.80	$21.80
Purchase #3	$31.93	5.307%	$33.6245	$33.62	$33.60	$33.60
Purchase #4	$82.38	4.222%	$85.8581	$85.86	$85.85	$85.90
Purchase #5	$112.55	13.831%	$128.1168	$128.12	$128.10	$128.10
Purchase #6	$170.83	9.226%	$186.5908	$186.59	$186.60	$186.60
Purchase #7	$56.49	4.231%	$58.8801	$58.88	$58.90	$58.90
7 purchase totals =	$593.21		$645.2701	$645.27	$645.25	$645.30