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	$203.49	11.699%	$227.2963	$227.30	$227.30	$227.30
Purchase #2	$42.88	13.182%	$48.5324	$48.53	$48.55	$48.50
Purchase #3	$181.52	3.105%	$187.1562	$187.16	$187.15	$187.20
Purchase #4	$96.48	3.529%	$99.8848	$99.88	$99.90	$99.90
Purchase #5	$207.81	5.199%	$218.614	$218.61	$218.60	$218.60
Purchase #6	$90.72	5.236%	$95.4701	$95.47	$95.45	$95.50
Purchase #7	$113.29	6.200%	$120.314	$120.31	$120.30	$120.30
7 purchase totals =	$936.19		$997.2678	$997.26	$997.25	$997.30