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	$62.45	3.218%	$64.4596	$64.46	$64.45	$64.50
Purchase #2	$99.37	13.361%	$112.6468	$112.65	$112.65	$112.60
Purchase #3	$7.40	5.649%	$7.818	$7.82	$7.80	$7.80
Purchase #4	$180.57	6.353%	$192.0416	$192.04	$192.05	$192.00
Purchase #5	$28.50	9.102%	$31.0941	$31.09	$31.10	$31.10
Purchase #6	$137.41	5.459%	$144.9112	$144.91	$144.90	$144.90
Purchase #7	$135.89	8.599%	$147.5752	$147.58	$147.60	$147.60
7 purchase totals =	$651.59		$700.5465	$700.55	$700.55	$700.50