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	$216.94	7.204%	$232.5684	$232.57	$232.55	$232.60
Purchase #2	$203.63	3.626%	$211.0136	$211.01	$211.00	$211.00
Purchase #3	$67.33	13.500%	$76.4196	$76.42	$76.40	$76.40
Purchase #4	$66.38	9.749%	$72.8514	$72.85	$72.85	$72.90
Purchase #5	$202.31	11.358%	$225.2884	$225.29	$225.30	$225.30
Purchase #6	$88.36	13.754%	$100.513	$100.51	$100.50	$100.50
Purchase #7	$164.25	9.433%	$179.7437	$179.74	$179.75	$179.70
7 purchase totals =	$1,009.20		$1,098.3981	$1,098.39	$1,098.35	$1,098.40