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	$117.64	11.565%	$131.2451	$131.25	$131.25	$131.20
Purchase #2	$241.84	11.637%	$269.9829	$269.98	$270.00	$270.00
Purchase #3	$158.35	3.692%	$164.1963	$164.20	$164.20	$164.20
Purchase #4	$64.29	11.372%	$71.6011	$71.60	$71.60	$71.60
Purchase #5	$15.96	8.592%	$17.3313	$17.33	$17.35	$17.30
Purchase #6	$106.74	10.361%	$117.7993	$117.80	$117.80	$117.80
Purchase #7	$176.90	11.146%	$196.6173	$196.62	$196.60	$196.60
7 purchase totals =	$881.72		$968.7733	$968.78	$968.80	$968.70