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	$166.61	3.749%	$172.8562	$172.86	$172.85	$172.90
Purchase #2	$180.58	12.761%	$203.6238	$203.62	$203.60	$203.60
Purchase #3	$17.63	4.701%	$18.4588	$18.46	$18.45	$18.50
Purchase #4	$133.89	6.362%	$142.4081	$142.41	$142.40	$142.40
Purchase #5	$189.82	13.600%	$215.6355	$215.64	$215.65	$215.60
Purchase #6	$144.45	12.536%	$162.5583	$162.56	$162.55	$162.60
Purchase #7	$42.56	13.639%	$48.3648	$48.36	$48.35	$48.40
7 purchase totals =	$875.54		$963.9055	$963.91	$963.85	$964.00