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	$213.75	8.595%	$232.1218	$232.12	$232.10	$232.10
Purchase #2	$177.96	5.821%	$188.3191	$188.32	$188.30	$188.30
Purchase #3	$42.60	11.472%	$47.4871	$47.49	$47.50	$47.50
Purchase #4	$67.25	9.423%	$73.587	$73.59	$73.60	$73.60
Purchase #5	$237.73	9.307%	$259.8555	$259.86	$259.85	$259.90
Purchase #6	$117.33	8.313%	$127.0836	$127.08	$127.10	$127.10
Purchase #7	$139.85	11.817%	$156.3761	$156.38	$156.40	$156.40
7 purchase totals =	$996.47		$1,084.8302	$1,084.84	$1,084.85	$1,084.90