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	$130.89	7.372%	$140.5392	$140.54	$140.55	$140.50
Purchase #2	$111.36	6.736%	$118.8612	$118.86	$118.85	$118.90
Purchase #3	$59.45	7.167%	$63.7108	$63.71	$63.70	$63.70
Purchase #4	$189.26	11.630%	$211.2709	$211.27	$211.25	$211.30
Purchase #5	$67.36	13.321%	$76.333	$76.33	$76.35	$76.30
Purchase #6	$85.85	12.245%	$96.3623	$96.36	$96.35	$96.40
Purchase #7	$134.34	4.553%	$140.4565	$140.46	$140.45	$140.50
7 purchase totals =	$778.51		$847.5339	$847.53	$847.50	$847.60