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	$14.56	10.749%	$16.1251	$16.13	$16.15	$16.10
Purchase #2	$88.57	12.281%	$99.4473	$99.45	$99.45	$99.40
Purchase #3	$162.29	8.191%	$175.5832	$175.58	$175.60	$175.60
Purchase #4	$75.28	11.475%	$83.9184	$83.92	$83.90	$83.90
Purchase #5	$130.97	11.383%	$145.8783	$145.88	$145.90	$145.90
Purchase #6	$98.45	11.712%	$109.9805	$109.98	$110.00	$110.00
Purchase #7	$90.62	11.517%	$101.0567	$101.06	$101.05	$101.10
7 purchase totals =	$660.74		$731.9895	$732.00	$732.05	$732.00