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	$102.72	11.742%	$114.7814	$114.78	$114.80	$114.80
Purchase #2	$84.81	12.279%	$95.2238	$95.22	$95.20	$95.20
Purchase #3	$134.92	6.206%	$143.2931	$143.29	$143.30	$143.30
Purchase #4	$209.57	4.469%	$218.9357	$218.94	$218.95	$218.90
Purchase #5	$115.38	10.163%	$127.1061	$127.11	$127.10	$127.10
Purchase #6	$169.60	11.768%	$189.5585	$189.56	$189.55	$189.60
Purchase #7	$166.77	11.460%	$185.8818	$185.88	$185.90	$185.90
7 purchase totals =	$983.77		$1,074.7804	$1,074.78	$1,074.80	$1,074.80