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	$161.34	4.585%	$168.7374	$168.74	$168.75	$168.70
Purchase #2	$236.50	5.217%	$248.8382	$248.84	$248.85	$248.80
Purchase #3	$109.93	6.678%	$117.2711	$117.27	$117.25	$117.30
Purchase #4	$63.65	13.609%	$72.3121	$72.31	$72.30	$72.30
Purchase #5	$107.61	9.661%	$118.0062	$118.01	$118.00	$118.00
Purchase #6	$70.81	9.359%	$77.4371	$77.44	$77.45	$77.40
Purchase #7	$192.98	6.863%	$206.2242	$206.22	$206.20	$206.20
7 purchase totals =	$942.82		$1,008.8263	$1,008.83	$1,008.80	$1,008.70