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	$122.44	9.697%	$134.313	$134.31	$134.30	$134.30
Purchase #2	$38.50	13.265%	$43.607	$43.61	$43.60	$43.60
Purchase #3	$198.32	11.850%	$221.8209	$221.82	$221.80	$221.80
Purchase #4	$30.81	7.551%	$33.1365	$33.14	$33.15	$33.10
Purchase #5	$238.87	10.700%	$264.4291	$264.43	$264.45	$264.40
Purchase #6	$108.43	5.167%	$114.0326	$114.03	$114.05	$114.00
Purchase #7	$63.89	12.606%	$71.944	$71.94	$71.95	$71.90
7 purchase totals =	$801.26		$883.2831	$883.28	$883.30	$883.10