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	$196.97	3.286%	$203.4424	$203.44	$203.45	$203.40
Purchase #2	$138.60	13.805%	$157.7337	$157.73	$157.75	$157.70
Purchase #3	$79.82	6.551%	$85.049	$85.05	$85.05	$85.00
Purchase #4	$188.83	12.228%	$211.9201	$211.92	$211.90	$211.90
Purchase #5	$91.26	10.250%	$100.6142	$100.61	$100.60	$100.60
Purchase #6	$103.91	7.688%	$111.8986	$111.90	$111.90	$111.90
Purchase #7	$92.75	9.663%	$101.7124	$101.71	$101.70	$101.70
7 purchase totals =	$892.14		$972.3704	$972.36	$972.35	$972.20