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	$76.60	9.147%	$83.6066	$83.61	$83.60	$83.60
Purchase #2	$154.96	9.571%	$169.7912	$169.79	$169.80	$169.80
Purchase #3	$174.34	3.782%	$180.9335	$180.93	$180.95	$180.90
Purchase #4	$226.31	3.797%	$234.903	$234.90	$234.90	$234.90
Purchase #5	$53.90	6.524%	$57.4164	$57.42	$57.40	$57.40
Purchase #6	$128.86	13.647%	$146.4455	$146.45	$146.45	$146.40
Purchase #7	$31.44	5.727%	$33.2406	$33.24	$33.25	$33.20
7 purchase totals =	$846.41		$906.3368	$906.34	$906.35	$906.20