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	$116.51	12.103%	$130.6112	$130.61	$130.60	$130.60
Purchase #2	$80.50	12.470%	$90.5384	$90.54	$90.55	$90.50
Purchase #3	$10.82	13.871%	$12.3208	$12.32	$12.30	$12.30
Purchase #4	$46.91	11.368%	$52.2427	$52.24	$52.25	$52.20
Purchase #5	$64.87	11.567%	$72.3735	$72.37	$72.35	$72.40
Purchase #6	$38.98	11.556%	$43.4845	$43.48	$43.50	$43.50
Purchase #7	$130.42	3.852%	$135.4438	$135.44	$135.45	$135.40
7 purchase totals =	$489.01		$537.0149	$537.00	$537.00	$536.90