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	$223.43	6.249%	$237.3921	$237.39	$237.40	$237.40
Purchase #2	$96.72	6.109%	$102.6286	$102.63	$102.65	$102.60
Purchase #3	$57.50	13.774%	$65.4201	$65.42	$65.40	$65.40
Purchase #4	$202.73	3.487%	$209.7992	$209.80	$209.80	$209.80
Purchase #5	$199.89	6.363%	$212.609	$212.61	$212.60	$212.60
Purchase #6	$100.83	5.579%	$106.4553	$106.46	$106.45	$106.50
Purchase #7	$171.25	7.746%	$184.515	$184.52	$184.50	$184.50
7 purchase totals =	$1,052.35		$1,118.8193	$1,118.83	$1,118.80	$1,118.80