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	$112.87	8.330%	$122.2721	$122.27	$122.25	$122.30
Purchase #2	$201.83	3.583%	$209.0616	$209.06	$209.05	$209.10
Purchase #3	$90.83	6.222%	$96.4814	$96.48	$96.50	$96.50
Purchase #4	$156.61	7.164%	$167.8295	$167.83	$167.85	$167.80
Purchase #5	$150.67	6.445%	$160.3807	$160.38	$160.40	$160.40
Purchase #6	$134.67	4.602%	$140.8675	$140.87	$140.85	$140.90
Purchase #7	$195.94	5.263%	$206.2523	$206.25	$206.25	$206.30
7 purchase totals =	$1,043.42		$1,103.1451	$1,103.14	$1,103.15	$1,103.30