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	$136.62	4.842%	$143.2351	$143.24	$143.25	$143.20
Purchase #2	$170.90	8.559%	$185.5273	$185.53	$185.55	$185.50
Purchase #3	$214.44	11.412%	$238.9119	$238.91	$238.90	$238.90
Purchase #4	$205.32	5.282%	$216.165	$216.17	$216.15	$216.20
Purchase #5	$69.45	12.523%	$78.1472	$78.15	$78.15	$78.10
Purchase #6	$64.90	7.757%	$69.9343	$69.93	$69.95	$69.90
Purchase #7	$197.59	10.521%	$218.3784	$218.38	$218.40	$218.40
7 purchase totals =	$1,059.22		$1,150.2992	$1,150.31	$1,150.35	$1,150.20