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	$98.92	10.332%	$109.1404	$109.14	$109.15	$109.10
Purchase #2	$168.42	6.351%	$179.1164	$179.12	$179.10	$179.10
Purchase #3	$64.50	11.792%	$72.1058	$72.11	$72.10	$72.10
Purchase #4	$65.38	12.312%	$73.4296	$73.43	$73.45	$73.40
Purchase #5	$234.80	8.208%	$254.0724	$254.07	$254.05	$254.10
Purchase #6	$120.84	11.215%	$134.3922	$134.39	$134.40	$134.40
Purchase #7	$166.62	11.732%	$186.1679	$186.17	$186.15	$186.20
7 purchase totals =	$919.48		$1,008.4247	$1,008.43	$1,008.40	$1,008.40