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	$217.33	11.870%	$243.1271	$243.13	$243.15	$243.10
Purchase #2	$235.67	6.300%	$250.5172	$250.52	$250.50	$250.50
Purchase #3	$92.84	6.504%	$98.8783	$98.88	$98.90	$98.90
Purchase #4	$96.55	7.173%	$103.4755	$103.48	$103.50	$103.50
Purchase #5	$13.81	13.274%	$15.6431	$15.64	$15.65	$15.60
Purchase #6	$189.82	5.345%	$199.9659	$199.97	$199.95	$200.00
Purchase #7	$12.34	8.397%	$13.3762	$13.38	$13.40	$13.40
7 purchase totals =	$858.36		$924.9833	$925.00	$925.05	$925.00