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	$211.93	12.726%	$238.9002	$238.90	$238.90	$238.90
Purchase #2	$176.95	11.739%	$197.7222	$197.72	$197.70	$197.70
Purchase #3	$178.42	4.663%	$186.7397	$186.74	$186.75	$186.70
Purchase #4	$58.78	5.360%	$61.9306	$61.93	$61.95	$61.90
Purchase #5	$99.38	5.558%	$104.9035	$104.90	$104.90	$104.90
Purchase #6	$20.93	5.133%	$22.0043	$22.00	$22.00	$22.00
Purchase #7	$114.47	7.864%	$123.4719	$123.47	$123.45	$123.50
7 purchase totals =	$860.86		$935.6724	$935.66	$935.65	$935.60