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	$148.91	13.529%	$169.056	$169.06	$169.05	$169.10
Purchase #2	$13.95	13.687%	$15.8593	$15.86	$15.85	$15.90
Purchase #3	$66.29	9.459%	$72.5604	$72.56	$72.55	$72.60
Purchase #4	$17.39	6.776%	$18.5683	$18.57	$18.55	$18.60
Purchase #5	$123.98	3.119%	$127.8469	$127.85	$127.85	$127.80
Purchase #6	$25.27	8.684%	$27.4644	$27.46	$27.45	$27.50
Purchase #7	$215.65	9.863%	$236.9196	$236.92	$236.90	$236.90
7 purchase totals =	$611.44		$668.2749	$668.28	$668.20	$668.40