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	$173.90	10.721%	$192.5438	$192.54	$192.55	$192.50
Purchase #2	$33.76	4.380%	$35.2387	$35.24	$35.25	$35.20
Purchase #3	$96.86	5.559%	$102.2444	$102.24	$102.25	$102.20
Purchase #4	$147.57	11.780%	$164.9537	$164.95	$164.95	$165.00
Purchase #5	$55.76	5.860%	$59.0275	$59.03	$59.05	$59.00
Purchase #6	$33.81	5.831%	$35.7815	$35.78	$35.80	$35.80
Purchase #7	$152.51	3.741%	$158.2154	$158.22	$158.20	$158.20
7 purchase totals =	$694.17		$748.0050	$748.00	$748.05	$747.90