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	$169.39	8.672%	$184.0795	$184.08	$184.10	$184.10
Purchase #2	$102.70	6.634%	$109.5131	$109.51	$109.50	$109.50
Purchase #3	$40.39	5.436%	$42.5856	$42.59	$42.60	$42.60
Purchase #4	$117.26	13.703%	$133.3281	$133.33	$133.35	$133.30
Purchase #5	$215.30	3.769%	$223.4147	$223.41	$223.40	$223.40
Purchase #6	$18.80	9.232%	$20.5356	$20.54	$20.55	$20.50
Purchase #7	$136.82	9.748%	$150.1572	$150.16	$150.15	$150.20
7 purchase totals =	$800.66		$863.6138	$863.62	$863.65	$863.60