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	$108.79	13.825%	$123.8302	$123.83	$123.85	$123.80
Purchase #2	$183.76	4.432%	$191.9042	$191.90	$191.90	$191.90
Purchase #3	$55.61	11.109%	$61.7877	$61.79	$61.80	$61.80
Purchase #4	$100.91	3.641%	$104.5841	$104.58	$104.60	$104.60
Purchase #5	$81.65	10.689%	$90.3776	$90.38	$90.40	$90.40
Purchase #6	$198.38	3.639%	$205.599	$205.60	$205.60	$205.60
Purchase #7	$86.29	13.134%	$97.6233	$97.62	$97.60	$97.60
7 purchase totals =	$815.39		$875.7061	$875.70	$875.75	$875.70