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	$130.93	10.388%	$144.531	$144.53	$144.55	$144.50
Purchase #2	$63.98	5.344%	$67.3991	$67.40	$67.40	$67.40
Purchase #3	$224.94	7.617%	$242.0737	$242.07	$242.05	$242.10
Purchase #4	$212.63	9.813%	$233.4954	$233.50	$233.50	$233.50
Purchase #5	$92.59	7.106%	$99.1694	$99.17	$99.15	$99.20
Purchase #6	$187.86	11.798%	$210.0237	$210.02	$210.00	$210.00
Purchase #7	$235.54	11.296%	$262.1466	$262.15	$262.15	$262.10
7 purchase totals =	$1,148.47		$1,258.8389	$1,258.84	$1,258.80	$1,258.80