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	$97.27	3.260%	$100.441	$100.44	$100.45	$100.40
Purchase #2	$157.32	9.777%	$172.7012	$172.70	$172.70	$172.70
Purchase #3	$64.81	12.296%	$72.779	$72.78	$72.80	$72.80
Purchase #4	$8.50	4.620%	$8.8927	$8.89	$8.90	$8.90
Purchase #5	$67.38	5.460%	$71.0589	$71.06	$71.05	$71.10
Purchase #6	$59.52	5.122%	$62.5686	$62.57	$62.55	$62.60
Purchase #7	$105.74	7.514%	$113.6853	$113.69	$113.70	$113.70
7 purchase totals =	$560.54		$602.1267	$602.13	$602.15	$602.20