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	$68.90	3.601%	$71.3811	$71.38	$71.40	$71.40
Purchase #2	$179.47	7.266%	$192.5103	$192.51	$192.50	$192.50
Purchase #3	$172.96	4.760%	$181.1929	$181.19	$181.20	$181.20
Purchase #4	$33.97	5.693%	$35.9039	$35.90	$35.90	$35.90
Purchase #5	$152.31	5.459%	$160.6246	$160.62	$160.60	$160.60
Purchase #6	$245.41	13.409%	$278.317	$278.32	$278.30	$278.30
Purchase #7	$144.78	3.823%	$150.3149	$150.31	$150.30	$150.30
7 purchase totals =	$997.80		$1,070.2447	$1,070.23	$1,070.20	$1,070.20