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	$147.86	7.796%	$159.3872	$159.39	$159.40	$159.40
Purchase #2	$192.37	13.543%	$218.4227	$218.42	$218.40	$218.40
Purchase #3	$221.32	13.239%	$250.6206	$250.62	$250.60	$250.60
Purchase #4	$142.59	12.223%	$160.0188	$160.02	$160.00	$160.00
Purchase #5	$192.53	11.867%	$215.3775	$215.38	$215.40	$215.40
Purchase #6	$33.69	8.237%	$36.465	$36.47	$36.45	$36.50
Purchase #7	$97.50	8.176%	$105.4716	$105.47	$105.45	$105.50
7 purchase totals =	$1,027.86		$1,145.7634	$1,145.77	$1,145.70	$1,145.80