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	$249.85	4.468%	$261.0133	$261.01	$261.00	$261.00
Purchase #2	$8.54	9.241%	$9.3292	$9.33	$9.35	$9.30
Purchase #3	$89.93	7.175%	$96.3825	$96.38	$96.40	$96.40
Purchase #4	$57.42	8.314%	$62.1939	$62.19	$62.20	$62.20
Purchase #5	$65.37	11.139%	$72.6516	$72.65	$72.65	$72.70
Purchase #6	$123.36	12.740%	$139.0761	$139.08	$139.10	$139.10
Purchase #7	$99.60	11.525%	$111.0789	$111.08	$111.10	$111.10
7 purchase totals =	$694.07		$751.7255	$751.72	$751.80	$751.80