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	$163.89	12.866%	$184.9761	$184.98	$185.00	$185.00
Purchase #2	$51.62	4.306%	$53.8428	$53.84	$53.85	$53.80
Purchase #3	$155.90	11.351%	$173.5962	$173.60	$173.60	$173.60
Purchase #4	$223.45	11.451%	$249.0373	$249.04	$249.05	$249.00
Purchase #5	$180.54	10.818%	$200.0708	$200.07	$200.05	$200.10
Purchase #6	$173.98	7.195%	$186.4979	$186.50	$186.50	$186.50
Purchase #7	$42.86	5.598%	$45.2593	$45.26	$45.25	$45.30
7 purchase totals =	$992.24		$1,093.2804	$1,093.29	$1,093.30	$1,093.30