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	$85.57	11.409%	$95.3327	$95.33	$95.35	$95.30
Purchase #2	$50.31	9.224%	$54.9506	$54.95	$54.95	$55.00
Purchase #3	$27.61	4.538%	$28.8629	$28.86	$28.85	$28.90
Purchase #4	$94.48	4.847%	$99.0594	$99.06	$99.05	$99.10
Purchase #5	$26.48	13.308%	$30.004	$30.00	$30.00	$30.00
Purchase #6	$30.56	3.595%	$31.6586	$31.66	$31.65	$31.70
Purchase #7	$71.59	9.821%	$78.6209	$78.62	$78.60	$78.60
7 purchase totals =	$386.60		$418.4891	$418.48	$418.45	$418.60