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	$90.91	4.860%	$95.3282	$95.33	$95.35	$95.30
Purchase #2	$95.68	11.352%	$106.5416	$106.54	$106.55	$106.50
Purchase #3	$119.69	6.571%	$127.5548	$127.55	$127.55	$127.60
Purchase #4	$31.80	8.143%	$34.3895	$34.39	$34.40	$34.40
Purchase #5	$174.47	10.271%	$192.3898	$192.39	$192.40	$192.40
Purchase #6	$80.44	11.526%	$89.7115	$89.71	$89.70	$89.70
Purchase #7	$64.87	13.264%	$73.4744	$73.47	$73.45	$73.50
7 purchase totals =	$657.86		$719.3898	$719.38	$719.40	$719.40