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	$75.63	8.801%	$82.2862	$82.29	$82.30	$82.30
Purchase #2	$94.57	10.670%	$104.6606	$104.66	$104.65	$104.70
Purchase #3	$120.70	8.814%	$131.3385	$131.34	$131.35	$131.30
Purchase #4	$37.53	3.341%	$38.7839	$38.78	$38.80	$38.80
Purchase #5	$17.53	4.428%	$18.3062	$18.31	$18.30	$18.30
Purchase #6	$179.43	7.206%	$192.3597	$192.36	$192.35	$192.40
Purchase #7	$222.47	6.746%	$237.4778	$237.48	$237.50	$237.50
7 purchase totals =	$747.86		$805.2129	$805.22	$805.25	$805.30