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	7.655%	$233.5468	$233.55	$233.55	$233.50
Purchase #2	$250.94	9.192%	$274.0064	$274.01	$274.00	$274.00
Purchase #3	$72.59	6.120%	$77.0325	$77.03	$77.05	$77.00
Purchase #4	$179.42	10.435%	$198.1425	$198.14	$198.15	$198.10
Purchase #5	$141.38	3.732%	$146.6563	$146.66	$146.65	$146.70
Purchase #6	$77.64	11.211%	$86.3442	$86.34	$86.35	$86.30
Purchase #7	$245.34	5.221%	$258.1492	$258.15	$258.15	$258.10
7 purchase totals =	$1,184.25		$1,273.8779	$1,273.88	$1,273.90	$1,273.70