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	$9.65	4.197%	$10.055	$10.06	$10.05	$10.10
Purchase #2	$187.43	6.474%	$199.5642	$199.56	$199.55	$199.60
Purchase #3	$150.32	4.363%	$156.8785	$156.88	$156.90	$156.90
Purchase #4	$84.89	5.807%	$89.8196	$89.82	$89.80	$89.80
Purchase #5	$160.93	5.824%	$170.3026	$170.30	$170.30	$170.30
Purchase #6	$100.50	4.537%	$105.0597	$105.06	$105.05	$105.10
Purchase #7	$50.91	5.691%	$53.8073	$53.81	$53.80	$53.80
7 purchase totals =	$744.63		$785.4869	$785.49	$785.45	$785.60