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	$53.71	10.628%	$59.4183	$59.42	$59.40	$59.40
Purchase #2	$207.38	12.643%	$233.5991	$233.60	$233.60	$233.60
Purchase #3	$6.99	6.192%	$7.4228	$7.42	$7.40	$7.40
Purchase #4	$55.37	13.508%	$62.8494	$62.85	$62.85	$62.80
Purchase #5	$220.37	11.355%	$245.393	$245.39	$245.40	$245.40
Purchase #6	$26.72	13.314%	$30.2775	$30.28	$30.30	$30.30
Purchase #7	$245.50	13.445%	$278.5075	$278.51	$278.50	$278.50
7 purchase totals =	$816.04		$917.4676	$917.47	$917.45	$917.40