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	$31.44	10.184%	$34.6418	$34.64	$34.65	$34.60
Purchase #2	$71.48	9.516%	$78.282	$78.28	$78.30	$78.30
Purchase #3	$184.95	6.417%	$196.8182	$196.82	$196.80	$196.80
Purchase #4	$130.48	10.637%	$144.3592	$144.36	$144.35	$144.40
Purchase #5	$83.35	3.122%	$85.9522	$85.95	$85.95	$86.00
Purchase #6	$32.98	9.795%	$36.2104	$36.21	$36.20	$36.20
Purchase #7	$131.80	3.775%	$136.7755	$136.78	$136.80	$136.80
7 purchase totals =	$666.48		$713.0393	$713.04	$713.05	$713.10