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	$94.30	6.188%	$100.1353	$100.14	$100.15	$100.10
Purchase #2	$67.43	7.675%	$72.6053	$72.61	$72.60	$72.60
Purchase #3	$61.49	12.594%	$69.2341	$69.23	$69.25	$69.20
Purchase #4	$115.65	13.574%	$131.3483	$131.35	$131.35	$131.30
Purchase #5	$57.92	7.217%	$62.1001	$62.10	$62.10	$62.10
Purchase #6	$76.39	11.808%	$85.4101	$85.41	$85.40	$85.40
Purchase #7	$181.66	11.134%	$201.886	$201.89	$201.90	$201.90
7 purchase totals =	$654.84		$722.7192	$722.73	$722.75	$722.60