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	$61.52	3.258%	$63.5243	$63.52	$63.50	$63.50
Purchase #2	$78.51	4.600%	$82.1215	$82.12	$82.10	$82.10
Purchase #3	$241.39	5.774%	$255.3279	$255.33	$255.35	$255.30
Purchase #4	$148.26	8.169%	$160.3714	$160.37	$160.35	$160.40
Purchase #5	$36.84	4.477%	$38.4893	$38.49	$38.50	$38.50
Purchase #6	$78.39	12.777%	$88.4059	$88.41	$88.40	$88.40
Purchase #7	$166.82	11.310%	$185.6873	$185.69	$185.70	$185.70
7 purchase totals =	$811.73		$873.9276	$873.93	$873.90	$873.90