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	$218.73	12.682%	$246.4693	$246.47	$246.45	$246.50
Purchase #2	$198.61	10.225%	$218.9179	$218.92	$218.90	$218.90
Purchase #3	$76.91	8.708%	$83.6073	$83.61	$83.60	$83.60
Purchase #4	$115.85	10.417%	$127.9181	$127.92	$127.90	$127.90
Purchase #5	$60.34	12.615%	$67.9519	$67.95	$67.95	$68.00
Purchase #6	$211.66	5.328%	$222.9372	$222.94	$222.95	$222.90
Purchase #7	$179.95	3.272%	$185.838	$185.84	$185.85	$185.80
7 purchase totals =	$1,062.05		$1,153.6397	$1,153.65	$1,153.60	$1,153.60