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	$177.41	4.531%	$185.4484	$185.45	$185.45	$185.40
Purchase #2	$92.73	10.484%	$102.4518	$102.45	$102.45	$102.50
Purchase #3	$19.92	7.869%	$21.4875	$21.49	$21.50	$21.50
Purchase #4	$229.83	13.284%	$260.3606	$260.36	$260.35	$260.40
Purchase #5	$5.94	8.102%	$6.4213	$6.42	$6.40	$6.40
Purchase #6	$82.87	4.323%	$86.4525	$86.45	$86.45	$86.50
Purchase #7	$47.61	3.865%	$49.4501	$49.45	$49.45	$49.50
7 purchase totals =	$656.31		$712.0722	$712.07	$712.05	$712.20