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	$116.51	10.335%	$128.5513	$128.55	$128.55	$128.60
Purchase #2	$187.86	11.558%	$209.5729	$209.57	$209.55	$209.60
Purchase #3	$96.83	12.838%	$109.261	$109.26	$109.25	$109.30
Purchase #4	$226.94	6.213%	$241.0398	$241.04	$241.05	$241.00
Purchase #5	$37.66	6.362%	$40.0559	$40.06	$40.05	$40.10
Purchase #6	$228.85	5.118%	$240.5625	$240.56	$240.55	$240.60
Purchase #7	$45.78	13.181%	$51.8143	$51.81	$51.80	$51.80
7 purchase totals =	$940.43		$1,020.8577	$1,020.85	$1,020.80	$1,021.00