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	$32.85	5.590%	$34.6863	$34.69	$34.70	$34.70
Purchase #2	$238.31	3.628%	$246.9559	$246.96	$246.95	$247.00
Purchase #3	$242.74	3.148%	$250.3815	$250.38	$250.40	$250.40
Purchase #4	$84.52	6.795%	$90.2631	$90.26	$90.25	$90.30
Purchase #5	$50.59	7.424%	$54.3458	$54.35	$54.35	$54.30
Purchase #6	$120.64	8.628%	$131.0488	$131.05	$131.05	$131.00
Purchase #7	$215.54	8.707%	$234.3071	$234.31	$234.30	$234.30
7 purchase totals =	$985.19		$1,041.9885	$1,042.00	$1,042.00	$1,042.00