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	$81.39	8.610%	$88.3977	$88.40	$88.40	$88.40
Purchase #2	$99.90	11.524%	$111.4125	$111.41	$111.40	$111.40
Purchase #3	$77.86	5.337%	$82.0154	$82.02	$82.00	$82.00
Purchase #4	$86.89	7.369%	$93.2929	$93.29	$93.30	$93.30
Purchase #5	$210.40	12.848%	$237.4322	$237.43	$237.45	$237.40
Purchase #6	$162.94	6.222%	$173.0781	$173.08	$173.10	$173.10
Purchase #7	$202.79	8.162%	$219.3417	$219.34	$219.35	$219.30
7 purchase totals =	$922.17		$1,004.9705	$1,004.97	$1,005.00	$1,004.90