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	$186.68	5.460%	$196.8727	$196.87	$196.85	$196.90
Purchase #2	$80.80	3.471%	$83.6046	$83.60	$83.60	$83.60
Purchase #3	$31.71	11.515%	$35.3614	$35.36	$35.35	$35.40
Purchase #4	$17.94	9.354%	$19.6181	$19.62	$19.60	$19.60
Purchase #5	$190.71	9.219%	$208.2916	$208.29	$208.30	$208.30
Purchase #6	$30.50	9.793%	$33.4869	$33.49	$33.50	$33.50
Purchase #7	$138.75	11.664%	$154.9338	$154.93	$154.95	$154.90
7 purchase totals =	$677.09		$732.1691	$732.16	$732.15	$732.20