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	$102.60	12.763%	$115.6948	$115.69	$115.70	$115.70
Purchase #2	$58.80	4.659%	$61.5395	$61.54	$61.55	$61.50
Purchase #3	$14.50	7.471%	$15.5833	$15.58	$15.60	$15.60
Purchase #4	$94.47	5.382%	$99.5544	$99.55	$99.55	$99.60
Purchase #5	$95.79	6.401%	$101.9215	$101.92	$101.90	$101.90
Purchase #6	$62.49	8.668%	$67.9066	$67.91	$67.90	$67.90
Purchase #7	$220.77	4.127%	$229.8812	$229.88	$229.90	$229.90
7 purchase totals =	$649.42		$692.0813	$692.07	$692.10	$692.10