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	$93.39	7.143%	$100.0608	$100.06	$100.05	$100.10
Purchase #2	$192.28	3.647%	$199.2925	$199.29	$199.30	$199.30
Purchase #3	$170.84	5.453%	$180.1559	$180.16	$180.15	$180.20
Purchase #4	$46.32	8.698%	$50.3489	$50.35	$50.35	$50.30
Purchase #5	$168.48	4.201%	$175.5578	$175.56	$175.55	$175.60
Purchase #6	$177.82	12.217%	$199.5443	$199.54	$199.55	$199.50
Purchase #7	$194.85	5.786%	$206.124	$206.12	$206.10	$206.10
7 purchase totals =	$1,043.98		$1,111.0842	$1,111.08	$1,111.05	$1,111.10