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	$57.64	4.602%	$60.2926	$60.29	$60.30	$60.30
Purchase #2	$222.31	12.401%	$249.8787	$249.88	$249.90	$249.90
Purchase #3	$99.61	4.621%	$104.213	$104.21	$104.20	$104.20
Purchase #4	$47.39	11.829%	$52.9958	$53.00	$53.00	$53.00
Purchase #5	$134.43	8.296%	$145.5823	$145.58	$145.60	$145.60
Purchase #6	$212.31	6.232%	$225.5412	$225.54	$225.55	$225.50
Purchase #7	$232.43	6.807%	$248.2515	$248.25	$248.25	$248.30
7 purchase totals =	$1,006.12		$1,086.7551	$1,086.75	$1,086.80	$1,086.80