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	$82.38	3.158%	$84.9816	$84.98	$85.00	$85.00
Purchase #2	$72.38	6.232%	$76.8907	$76.89	$76.90	$76.90
Purchase #3	$113.97	11.139%	$126.6651	$126.67	$126.65	$126.70
Purchase #4	$158.62	4.361%	$165.5374	$165.54	$165.55	$165.50
Purchase #5	$147.94	8.523%	$160.5489	$160.55	$160.55	$160.50
Purchase #6	$65.85	8.463%	$71.4229	$71.42	$71.40	$71.40
Purchase #7	$138.56	8.298%	$150.0577	$150.06	$150.05	$150.10
7 purchase totals =	$779.70		$836.1043	$836.11	$836.10	$836.10