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	$192.76	13.393%	$218.5763	$218.58	$218.60	$218.60
Purchase #2	$35.65	12.396%	$40.0692	$40.07	$40.05	$40.10
Purchase #3	$151.69	3.143%	$156.4576	$156.46	$156.45	$156.50
Purchase #4	$99.73	13.193%	$112.8874	$112.89	$112.90	$112.90
Purchase #5	$223.43	7.515%	$240.2208	$240.22	$240.20	$240.20
Purchase #6	$194.57	8.659%	$211.4178	$211.42	$211.40	$211.40
Purchase #7	$180.93	9.860%	$198.7697	$198.77	$198.75	$198.80
7 purchase totals =	$1,078.76		$1,178.3988	$1,178.41	$1,178.35	$1,178.50