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	$82.99	7.853%	$89.5072	$89.51	$89.50	$89.50
Purchase #2	$18.41	3.387%	$19.0335	$19.03	$19.05	$19.00
Purchase #3	$89.43	7.588%	$96.2159	$96.22	$96.20	$96.20
Purchase #4	$112.44	3.683%	$116.5812	$116.58	$116.60	$116.60
Purchase #5	$88.34	4.150%	$92.0061	$92.01	$92.00	$92.00
Purchase #6	$82.33	5.852%	$87.148	$87.15	$87.15	$87.10
Purchase #7	$154.92	11.441%	$172.6444	$172.64	$172.65	$172.60
7 purchase totals =	$628.86		$673.1363	$673.14	$673.15	$673.00