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	$186.68	7.225%	$200.1676	$200.17	$200.15	$200.20
Purchase #2	$88.86	12.426%	$99.9017	$99.90	$99.90	$99.90
Purchase #3	$97.49	6.410%	$103.7391	$103.74	$103.75	$103.70
Purchase #4	$94.90	8.652%	$103.1107	$103.11	$103.10	$103.10
Purchase #5	$82.49	3.226%	$85.1511	$85.15	$85.15	$85.20
Purchase #6	$248.56	5.316%	$261.7734	$261.77	$261.75	$261.80
Purchase #7	$202.92	12.716%	$228.7233	$228.72	$228.70	$228.70
7 purchase totals =	$1,001.90		$1,082.5669	$1,082.56	$1,082.50	$1,082.60