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	$152.64	13.730%	$173.5975	$173.60	$173.60	$173.60
Purchase #2	$80.36	6.663%	$85.7144	$85.71	$85.70	$85.70
Purchase #3	$27.29	9.434%	$29.8645	$29.86	$29.85	$29.90
Purchase #4	$204.33	7.576%	$219.81	$219.81	$219.80	$219.80
Purchase #5	$140.72	10.429%	$155.3957	$155.40	$155.40	$155.40
Purchase #6	$104.83	4.793%	$109.8545	$109.85	$109.85	$109.90
Purchase #7	$138.65	8.861%	$150.9358	$150.94	$150.95	$150.90
7 purchase totals =	$848.82		$925.1724	$925.17	$925.15	$925.20