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	$63.90	13.446%	$72.492	$72.49	$72.50	$72.50
Purchase #2	$50.70	3.140%	$52.292	$52.29	$52.30	$52.30
Purchase #3	$93.57	3.209%	$96.5727	$96.57	$96.55	$96.60
Purchase #4	$85.38	3.172%	$88.0883	$88.09	$88.10	$88.10
Purchase #5	$87.47	12.599%	$98.4903	$98.49	$98.50	$98.50
Purchase #6	$151.32	4.117%	$157.5498	$157.55	$157.55	$157.50
Purchase #7	$5.48	13.282%	$6.2079	$6.21	$6.20	$6.20
7 purchase totals =	$537.82		$571.6930	$571.69	$571.70	$571.70