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	$182.51	8.790%	$198.5526	$198.55	$198.55	$198.60
Purchase #2	$136.75	6.778%	$146.0189	$146.02	$146.00	$146.00
Purchase #3	$65.37	7.873%	$70.5166	$70.52	$70.50	$70.50
Purchase #4	$129.27	6.171%	$137.2473	$137.25	$137.25	$137.20
Purchase #5	$143.79	8.527%	$156.051	$156.05	$156.05	$156.10
Purchase #6	$201.59	4.182%	$210.0205	$210.02	$210.00	$210.00
Purchase #7	$83.70	7.436%	$89.9239	$89.92	$89.90	$89.90
7 purchase totals =	$942.98		$1,008.3308	$1,008.33	$1,008.25	$1,008.30