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	$152.39	11.771%	$170.3278	$170.33	$170.35	$170.30
Purchase #2	$57.96	7.435%	$62.2693	$62.27	$62.25	$62.30
Purchase #3	$233.48	7.801%	$251.6938	$251.69	$251.70	$251.70
Purchase #4	$140.43	11.289%	$156.2831	$156.28	$156.30	$156.30
Purchase #5	$118.94	3.464%	$123.0601	$123.06	$123.05	$123.10
Purchase #6	$160.63	11.106%	$178.4696	$178.47	$178.45	$178.50
Purchase #7	$102.49	8.678%	$111.3841	$111.38	$111.40	$111.40
7 purchase totals =	$966.32		$1,053.4878	$1,053.48	$1,053.50	$1,053.60