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	$198.85	4.394%	$207.5875	$207.59	$207.60	$207.60
Purchase #2	$91.67	8.655%	$99.604	$99.60	$99.60	$99.60
Purchase #3	$221.88	10.356%	$244.8579	$244.86	$244.85	$244.90
Purchase #4	$178.89	12.321%	$200.931	$200.93	$200.95	$200.90
Purchase #5	$24.83	9.135%	$27.0982	$27.10	$27.10	$27.10
Purchase #6	$222.35	7.368%	$238.7327	$238.73	$238.75	$238.70
Purchase #7	$92.31	13.163%	$104.4608	$104.46	$104.45	$104.50
7 purchase totals =	$1,030.78		$1,123.2721	$1,123.27	$1,123.30	$1,123.30