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	$168.74	10.423%	$186.3278	$186.33	$186.35	$186.30
Purchase #2	$127.72	13.794%	$145.3377	$145.34	$145.35	$145.30
Purchase #3	$37.32	13.464%	$42.3448	$42.34	$42.35	$42.30
Purchase #4	$16.96	8.192%	$18.3494	$18.35	$18.35	$18.30
Purchase #5	$100.61	10.671%	$111.3461	$111.35	$111.35	$111.30
Purchase #6	$184.71	3.289%	$190.7851	$190.79	$190.80	$190.80
Purchase #7	$87.61	4.371%	$91.4394	$91.44	$91.45	$91.40
7 purchase totals =	$723.67		$785.9303	$785.94	$786.00	$785.70