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	$99.27	7.729%	$106.9426	$106.94	$106.95	$106.90
Purchase #2	$81.32	13.223%	$92.0729	$92.07	$92.05	$92.10
Purchase #3	$6.71	9.449%	$7.344	$7.34	$7.35	$7.30
Purchase #4	$67.61	5.780%	$71.5179	$71.52	$71.50	$71.50
Purchase #5	$16.38	10.126%	$18.0386	$18.04	$18.05	$18.00
Purchase #6	$125.75	13.392%	$142.5904	$142.59	$142.60	$142.60
Purchase #7	$247.64	5.775%	$261.9412	$261.94	$261.95	$261.90
7 purchase totals =	$644.68		$700.4476	$700.44	$700.45	$700.30