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	$49.54	7.135%	$53.0747	$53.07	$53.05	$53.10
Purchase #2	$89.75	10.630%	$99.2904	$99.29	$99.30	$99.30
Purchase #3	$95.84	9.188%	$104.6458	$104.65	$104.65	$104.60
Purchase #4	$237.62	3.426%	$245.7609	$245.76	$245.75	$245.80
Purchase #5	$179.62	11.246%	$199.8201	$199.82	$199.80	$199.80
Purchase #6	$238.78	5.180%	$251.1488	$251.15	$251.15	$251.10
Purchase #7	$63.97	3.554%	$66.2435	$66.24	$66.25	$66.20
7 purchase totals =	$955.12		$1,019.9842	$1,019.98	$1,019.95	$1,019.90