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	$97.91	11.591%	$109.2587	$109.26	$109.25	$109.30
Purchase #2	$62.75	7.302%	$67.332	$67.33	$67.35	$67.30
Purchase #3	$95.99	13.316%	$108.772	$108.77	$108.75	$108.80
Purchase #4	$79.79	3.337%	$82.4526	$82.45	$82.45	$82.50
Purchase #5	$105.98	7.619%	$114.0546	$114.05	$114.05	$114.10
Purchase #6	$154.85	10.666%	$171.3663	$171.37	$171.35	$171.40
Purchase #7	$92.81	6.693%	$99.0218	$99.02	$99.00	$99.00
7 purchase totals =	$690.08		$752.2580	$752.25	$752.20	$752.40