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	$104.59	5.312%	$110.1458	$110.15	$110.15	$110.10
Purchase #2	$206.67	13.515%	$234.6015	$234.60	$234.60	$234.60
Purchase #3	$215.96	11.864%	$241.5815	$241.58	$241.60	$241.60
Purchase #4	$100.56	9.139%	$109.7502	$109.75	$109.75	$109.80
Purchase #5	$170.35	10.286%	$187.8722	$187.87	$187.85	$187.90
Purchase #6	$53.65	10.116%	$59.0772	$59.08	$59.10	$59.10
Purchase #7	$58.29	8.290%	$63.1222	$63.12	$63.10	$63.10
7 purchase totals =	$910.07		$1,006.1506	$1,006.15	$1,006.15	$1,006.20