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	$99.32	8.776%	$108.0363	$108.04	$108.05	$108.00
Purchase #2	$116.94	9.743%	$128.3335	$128.33	$128.35	$128.30
Purchase #3	$67.39	12.867%	$76.0611	$76.06	$76.05	$76.10
Purchase #4	$7.90	4.687%	$8.2703	$8.27	$8.25	$8.30
Purchase #5	$147.46	13.432%	$167.2668	$167.27	$167.25	$167.30
Purchase #6	$172.33	11.865%	$192.777	$192.78	$192.80	$192.80
Purchase #7	$40.27	13.327%	$45.6368	$45.64	$45.65	$45.60
7 purchase totals =	$651.61		$726.3818	$726.39	$726.40	$726.40