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	$135.60	3.561%	$140.4287	$140.43	$140.45	$140.40
Purchase #2	$204.59	4.273%	$213.3321	$213.33	$213.35	$213.30
Purchase #3	$190.33	9.319%	$208.0669	$208.07	$208.05	$208.10
Purchase #4	$193.78	13.492%	$219.9248	$219.92	$219.90	$219.90
Purchase #5	$167.43	6.557%	$178.4084	$178.41	$178.40	$178.40
Purchase #6	$33.98	3.502%	$35.17	$35.17	$35.15	$35.20
Purchase #7	$135.71	10.685%	$150.2106	$150.21	$150.20	$150.20
7 purchase totals =	$1,061.42		$1,145.5415	$1,145.54	$1,145.50	$1,145.50