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	$64.46	3.801%	$66.9101	$66.91	$66.90	$66.90
Purchase #2	$205.94	10.742%	$228.0621	$228.06	$228.05	$228.10
Purchase #3	$7.31	4.682%	$7.6523	$7.65	$7.65	$7.70
Purchase #4	$233.30	10.841%	$258.5921	$258.59	$258.60	$258.60
Purchase #5	$209.28	4.681%	$219.0764	$219.08	$219.10	$219.10
Purchase #6	$95.32	3.706%	$98.8526	$98.85	$98.85	$98.90
Purchase #7	$173.63	9.198%	$189.6005	$189.60	$189.60	$189.60
7 purchase totals =	$989.24		$1,068.7461	$1,068.74	$1,068.75	$1,068.90