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	$169.62	10.506%	$187.4403	$187.44	$187.45	$187.40
Purchase #2	$38.28	11.163%	$42.5532	$42.55	$42.55	$42.60
Purchase #3	$203.56	6.342%	$216.4698	$216.47	$216.45	$216.50
Purchase #4	$71.26	8.819%	$77.5444	$77.54	$77.55	$77.50
Purchase #5	$179.57	9.229%	$196.1425	$196.14	$196.15	$196.10
Purchase #6	$63.46	8.700%	$68.981	$68.98	$69.00	$69.00
Purchase #7	$10.34	13.156%	$11.7003	$11.70	$11.70	$11.70
7 purchase totals =	$736.09		$800.8315	$800.82	$800.85	$800.80