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	$63.41	4.642%	$66.3535	$66.35	$66.35	$66.40
Purchase #2	$246.77	7.505%	$265.2901	$265.29	$265.30	$265.30
Purchase #3	$85.43	7.686%	$91.9961	$92.00	$92.00	$92.00
Purchase #4	$82.52	8.508%	$89.5408	$89.54	$89.55	$89.50
Purchase #5	$152.78	3.562%	$158.222	$158.22	$158.20	$158.20
Purchase #6	$126.61	6.570%	$134.9283	$134.93	$134.95	$134.90
Purchase #7	$96.29	8.139%	$104.127	$104.13	$104.15	$104.10
7 purchase totals =	$853.81		$910.4578	$910.46	$910.50	$910.40