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	$40.50	11.317%	$45.0834	$45.08	$45.10	$45.10
Purchase #2	$27.27	7.578%	$29.3365	$29.34	$29.35	$29.30
Purchase #3	$205.26	13.459%	$232.8859	$232.89	$232.90	$232.90
Purchase #4	$182.32	7.717%	$196.3896	$196.39	$196.40	$196.40
Purchase #5	$234.93	12.388%	$264.0331	$264.03	$264.05	$264.00
Purchase #6	$97.41	10.676%	$107.8095	$107.81	$107.80	$107.80
Purchase #7	$146.32	3.172%	$150.9613	$150.96	$150.95	$151.00
7 purchase totals =	$934.01		$1,026.4993	$1,026.50	$1,026.55	$1,026.50