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	$183.41	9.227%	$200.3332	$200.33	$200.35	$200.30
Purchase #2	$5.39	7.521%	$5.7954	$5.80	$5.80	$5.80
Purchase #3	$97.30	9.196%	$106.2477	$106.25	$106.25	$106.20
Purchase #4	$124.55	12.370%	$139.9568	$139.96	$139.95	$140.00
Purchase #5	$85.93	4.611%	$89.8922	$89.89	$89.90	$89.90
Purchase #6	$124.52	5.807%	$131.7509	$131.75	$131.75	$131.80
Purchase #7	$247.54	6.491%	$263.6078	$263.61	$263.60	$263.60
7 purchase totals =	$868.64		$937.5840	$937.59	$937.60	$937.60