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	$237.90	10.274%	$262.3418	$262.34	$262.35	$262.30
Purchase #2	$227.71	13.498%	$258.4463	$258.45	$258.45	$258.40
Purchase #3	$100.90	8.391%	$109.3665	$109.37	$109.35	$109.40
Purchase #4	$17.88	3.150%	$18.4432	$18.44	$18.45	$18.40
Purchase #5	$151.81	13.826%	$172.7993	$172.80	$172.80	$172.80
Purchase #6	$191.48	8.173%	$207.1297	$207.13	$207.15	$207.10
Purchase #7	$68.36	4.410%	$71.3747	$71.37	$71.35	$71.40
7 purchase totals =	$996.04		$1,099.9015	$1,099.90	$1,099.90	$1,099.80