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	$26.88	9.672%	$29.4798	$29.48	$29.50	$29.50
Purchase #2	$64.90	4.584%	$67.875	$67.88	$67.90	$67.90
Purchase #3	$74.29	11.588%	$82.8987	$82.90	$82.90	$82.90
Purchase #4	$136.86	11.261%	$152.2718	$152.27	$152.25	$152.30
Purchase #5	$244.26	12.296%	$274.2942	$274.29	$274.30	$274.30
Purchase #6	$195.92	3.431%	$202.642	$202.64	$202.65	$202.60
Purchase #7	$111.74	11.432%	$124.5141	$124.51	$124.50	$124.50
7 purchase totals =	$854.85		$933.9756	$933.97	$934.00	$934.00