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	$182.84	9.643%	$200.4713	$200.47	$200.45	$200.50
Purchase #2	$94.59	11.464%	$105.4338	$105.43	$105.45	$105.40
Purchase #3	$152.29	4.265%	$158.7852	$158.79	$158.80	$158.80
Purchase #4	$34.35	4.456%	$35.8806	$35.88	$35.90	$35.90
Purchase #5	$25.64	11.376%	$28.5568	$28.56	$28.55	$28.60
Purchase #6	$19.36	6.513%	$20.6209	$20.62	$20.60	$20.60
Purchase #7	$234.56	10.134%	$258.3303	$258.33	$258.35	$258.30
7 purchase totals =	$743.63		$808.0789	$808.08	$808.10	$808.10