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	$211.46	12.570%	$238.0405	$238.04	$238.05	$238.00
Purchase #2	$56.90	8.819%	$61.918	$61.92	$61.90	$61.90
Purchase #3	$59.52	11.470%	$66.3469	$66.35	$66.35	$66.30
Purchase #4	$52.52	9.383%	$57.448	$57.45	$57.45	$57.40
Purchase #5	$65.48	6.714%	$69.8763	$69.88	$69.90	$69.90
Purchase #6	$179.78	9.787%	$197.3751	$197.38	$197.40	$197.40
Purchase #7	$132.65	3.723%	$137.5886	$137.59	$137.60	$137.60
7 purchase totals =	$758.31		$828.5934	$828.61	$828.65	$828.50