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	$176.48	12.536%	$198.6035	$198.60	$198.60	$198.60
Purchase #2	$22.49	3.491%	$23.2751	$23.28	$23.30	$23.30
Purchase #3	$56.49	8.623%	$61.3611	$61.36	$61.35	$61.40
Purchase #4	$62.98	5.237%	$66.2783	$66.28	$66.30	$66.30
Purchase #5	$104.59	6.220%	$111.0955	$111.10	$111.10	$111.10
Purchase #6	$102.67	6.359%	$109.1988	$109.20	$109.20	$109.20
Purchase #7	$136.88	3.666%	$141.898	$141.90	$141.90	$141.90
7 purchase totals =	$662.58		$711.7103	$711.72	$711.75	$711.80