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	$204.44	12.634%	$230.2689	$230.27	$230.25	$230.30
Purchase #2	$34.64	7.179%	$37.1268	$37.13	$37.15	$37.10
Purchase #3	$67.62	6.200%	$71.8124	$71.81	$71.80	$71.80
Purchase #4	$52.82	4.769%	$55.339	$55.34	$55.35	$55.30
Purchase #5	$21.69	3.656%	$22.483	$22.48	$22.50	$22.50
Purchase #6	$142.84	6.351%	$151.9118	$151.91	$151.90	$151.90
Purchase #7	$102.62	6.202%	$108.9845	$108.98	$109.00	$109.00
7 purchase totals =	$626.67		$677.9264	$677.92	$677.95	$677.90