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	$221.71	9.578%	$242.9454	$242.95	$242.95	$242.90
Purchase #2	$110.72	12.428%	$124.4803	$124.48	$124.50	$124.50
Purchase #3	$141.50	11.504%	$157.7782	$157.78	$157.80	$157.80
Purchase #4	$235.64	8.331%	$255.2712	$255.27	$255.25	$255.30
Purchase #5	$152.42	10.168%	$167.9181	$167.92	$167.90	$167.90
Purchase #6	$153.37	10.777%	$169.8987	$169.90	$169.90	$169.90
Purchase #7	$86.43	3.366%	$89.3392	$89.34	$89.35	$89.30
7 purchase totals =	$1,101.79		$1,207.6311	$1,207.64	$1,207.65	$1,207.60