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	$192.52	7.861%	$207.654	$207.65	$207.65	$207.70
Purchase #2	$174.28	3.863%	$181.0124	$181.01	$181.00	$181.00
Purchase #3	$123.94	6.419%	$131.8957	$131.90	$131.90	$131.90
Purchase #4	$250.30	12.475%	$281.5249	$281.52	$281.50	$281.50
Purchase #5	$60.62	4.192%	$63.1612	$63.16	$63.15	$63.20
Purchase #6	$52.56	12.506%	$59.1332	$59.13	$59.15	$59.10
Purchase #7	$19.86	3.367%	$20.5287	$20.53	$20.55	$20.50
7 purchase totals =	$874.08		$944.9101	$944.90	$944.90	$944.90