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	$85.86	3.844%	$89.1605	$89.16	$89.15	$89.20
Purchase #2	$135.87	12.801%	$153.2627	$153.26	$153.25	$153.30
Purchase #3	$228.45	5.863%	$241.844	$241.84	$241.85	$241.80
Purchase #4	$230.97	11.813%	$258.2545	$258.25	$258.25	$258.30
Purchase #5	$82.28	12.351%	$92.4424	$92.44	$92.45	$92.40
Purchase #6	$31.31	8.741%	$34.0468	$34.05	$34.05	$34.00
Purchase #7	$166.59	9.449%	$182.3311	$182.33	$182.35	$182.30
7 purchase totals =	$961.33		$1,051.3420	$1,051.33	$1,051.35	$1,051.30