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	$134.53	13.373%	$152.5207	$152.52	$152.50	$152.50
Purchase #2	$217.81	11.509%	$242.8778	$242.88	$242.90	$242.90
Purchase #3	$161.84	4.299%	$168.7975	$168.80	$168.80	$168.80
Purchase #4	$39.38	7.640%	$42.3886	$42.39	$42.40	$42.40
Purchase #5	$31.42	7.754%	$33.8563	$33.86	$33.85	$33.90
Purchase #6	$149.41	10.649%	$165.3207	$165.32	$165.30	$165.30
Purchase #7	$233.84	6.748%	$249.6195	$249.62	$249.60	$249.60
7 purchase totals =	$968.23		$1,055.3811	$1,055.39	$1,055.35	$1,055.40