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	$152.91	12.765%	$172.429	$172.43	$172.45	$172.40
Purchase #2	$90.45	12.717%	$101.9525	$101.95	$101.95	$102.00
Purchase #3	$156.88	11.435%	$174.8192	$174.82	$174.80	$174.80
Purchase #4	$202.90	10.351%	$223.9022	$223.90	$223.90	$223.90
Purchase #5	$18.34	10.653%	$20.2938	$20.29	$20.30	$20.30
Purchase #6	$92.86	3.230%	$95.8594	$95.86	$95.85	$95.90
Purchase #7	$203.49	12.372%	$228.6658	$228.67	$228.65	$228.70
7 purchase totals =	$917.83		$1,017.9219	$1,017.92	$1,017.90	$1,018.00