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	$81.93	9.261%	$89.5175	$89.52	$89.50	$89.50
Purchase #2	$43.26	11.336%	$48.164	$48.16	$48.15	$48.20
Purchase #3	$97.57	6.452%	$103.8652	$103.87	$103.85	$103.90
Purchase #4	$198.53	9.108%	$216.6121	$216.61	$216.60	$216.60
Purchase #5	$96.97	8.413%	$105.1281	$105.13	$105.15	$105.10
Purchase #6	$240.93	12.669%	$271.4534	$271.45	$271.45	$271.50
Purchase #7	$91.99	5.863%	$97.3834	$97.38	$97.40	$97.40
7 purchase totals =	$851.18		$932.1237	$932.12	$932.10	$932.20