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	$101.36	7.572%	$109.035	$109.04	$109.05	$109.00
Purchase #2	$204.47	13.869%	$232.8279	$232.83	$232.85	$232.80
Purchase #3	$200.57	12.389%	$225.4186	$225.42	$225.40	$225.40
Purchase #4	$187.61	10.542%	$207.3878	$207.39	$207.40	$207.40
Purchase #5	$219.59	10.814%	$243.3365	$243.34	$243.35	$243.30
Purchase #6	$75.78	10.312%	$83.5944	$83.59	$83.60	$83.60
Purchase #7	$183.39	8.638%	$199.2312	$199.23	$199.25	$199.20
7 purchase totals =	$1,172.77		$1,300.8314	$1,300.84	$1,300.90	$1,300.70