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	$220.81	6.377%	$234.8911	$234.89	$234.90	$234.90
Purchase #2	$185.59	5.759%	$196.2781	$196.28	$196.30	$196.30
Purchase #3	$101.34	6.297%	$107.7214	$107.72	$107.70	$107.70
Purchase #4	$93.89	13.669%	$106.7238	$106.72	$106.70	$106.70
Purchase #5	$196.94	8.330%	$213.3451	$213.35	$213.35	$213.30
Purchase #6	$100.69	8.843%	$109.594	$109.59	$109.60	$109.60
Purchase #7	$208.44	5.245%	$219.3727	$219.37	$219.35	$219.40
7 purchase totals =	$1,107.70		$1,187.9262	$1,187.92	$1,187.90	$1,187.90