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	$37.45	7.700%	$40.3337	$40.33	$40.35	$40.30
Purchase #2	$157.73	5.438%	$166.3074	$166.31	$166.30	$166.30
Purchase #3	$233.38	11.554%	$260.3447	$260.34	$260.35	$260.30
Purchase #4	$180.60	9.784%	$198.2699	$198.27	$198.25	$198.30
Purchase #5	$101.44	11.214%	$112.8155	$112.82	$112.80	$112.80
Purchase #6	$53.49	3.252%	$55.2295	$55.23	$55.25	$55.20
Purchase #7	$172.83	11.745%	$193.1289	$193.13	$193.15	$193.10
7 purchase totals =	$936.92		$1,026.4296	$1,026.43	$1,026.45	$1,026.30