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	$83.25	7.252%	$89.2873	$89.29	$89.30	$89.30
Purchase #2	$169.82	6.745%	$181.2744	$181.27	$181.25	$181.30
Purchase #3	$131.51	7.598%	$141.5021	$141.50	$141.50	$141.50
Purchase #4	$250.29	10.538%	$276.6656	$276.67	$276.65	$276.70
Purchase #5	$174.79	3.600%	$181.0824	$181.08	$181.10	$181.10
Purchase #6	$80.54	6.694%	$85.9313	$85.93	$85.95	$85.90
Purchase #7	$64.45	8.467%	$69.907	$69.91	$69.90	$69.90
7 purchase totals =	$954.65		$1,025.6501	$1,025.65	$1,025.65	$1,025.70