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	5.834%	$215.3616	$215.36	$215.35	$215.40
Purchase #2	$96.63	4.129%	$100.6199	$100.62	$100.60	$100.60
Purchase #3	$92.54	6.240%	$98.3145	$98.31	$98.30	$98.30
Purchase #4	$207.47	4.256%	$216.2999	$216.30	$216.30	$216.30
Purchase #5	$32.35	12.337%	$36.341	$36.34	$36.35	$36.30
Purchase #6	$42.75	13.322%	$48.4452	$48.45	$48.45	$48.40
Purchase #7	$172.78	6.728%	$184.4046	$184.40	$184.40	$184.40
7 purchase totals =	$848.01		$899.7867	$899.78	$899.75	$899.70