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	$186.45	4.129%	$194.1485	$194.15	$194.15	$194.10
Purchase #2	$47.98	10.542%	$53.0381	$53.04	$53.05	$53.00
Purchase #3	$206.51	11.556%	$230.3743	$230.37	$230.35	$230.40
Purchase #4	$130.74	7.745%	$140.8658	$140.87	$140.85	$140.90
Purchase #5	$99.77	10.834%	$110.5791	$110.58	$110.60	$110.60
Purchase #6	$99.90	9.802%	$109.6922	$109.69	$109.70	$109.70
Purchase #7	$89.27	11.324%	$99.3789	$99.38	$99.40	$99.40
7 purchase totals =	$860.62		$938.0769	$938.08	$938.10	$938.10