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	$183.58	5.228%	$193.1776	$193.18	$193.20	$193.20
Purchase #2	$89.52	12.391%	$100.6124	$100.61	$100.60	$100.60
Purchase #3	$166.88	11.743%	$186.4767	$186.48	$186.50	$186.50
Purchase #4	$185.56	3.115%	$191.3402	$191.34	$191.35	$191.30
Purchase #5	$123.69	5.798%	$130.8615	$130.86	$130.85	$130.90
Purchase #6	$79.79	9.728%	$87.552	$87.55	$87.55	$87.60
Purchase #7	$103.66	5.517%	$109.3789	$109.38	$109.40	$109.40
7 purchase totals =	$932.68		$999.3993	$999.40	$999.45	$999.50