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	$117.50	8.174%	$127.1045	$127.10	$127.10	$127.10
Purchase #2	$16.57	11.270%	$18.4374	$18.44	$18.45	$18.40
Purchase #3	$13.59	7.574%	$14.6193	$14.62	$14.60	$14.60
Purchase #4	$147.31	5.491%	$155.3988	$155.40	$155.40	$155.40
Purchase #5	$69.26	5.816%	$73.2882	$73.29	$73.30	$73.30
Purchase #6	$19.76	10.751%	$21.8844	$21.88	$21.90	$21.90
Purchase #7	$39.44	7.829%	$42.5278	$42.53	$42.55	$42.50
7 purchase totals =	$423.43		$453.2604	$453.26	$453.30	$453.20