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	$68.65	11.183%	$76.3271	$76.33	$76.35	$76.30
Purchase #2	$166.25	4.132%	$173.1195	$173.12	$173.10	$173.10
Purchase #3	$172.52	13.620%	$196.0172	$196.02	$196.00	$196.00
Purchase #4	$11.89	13.413%	$13.4848	$13.48	$13.50	$13.50
Purchase #5	$54.97	4.280%	$57.3227	$57.32	$57.30	$57.30
Purchase #6	$61.70	12.816%	$69.6075	$69.61	$69.60	$69.60
Purchase #7	$181.25	3.645%	$187.8566	$187.86	$187.85	$187.90
7 purchase totals =	$717.23		$773.7354	$773.74	$773.70	$773.70