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	$167.70	3.624%	$173.7774	$173.78	$173.80	$173.80
Purchase #2	$230.57	12.196%	$258.6903	$258.69	$258.70	$258.70
Purchase #3	$39.83	9.450%	$43.5939	$43.59	$43.60	$43.60
Purchase #4	$24.27	8.588%	$26.3543	$26.35	$26.35	$26.40
Purchase #5	$150.62	7.853%	$162.4482	$162.45	$162.45	$162.40
Purchase #6	$98.83	11.179%	$109.8782	$109.88	$109.90	$109.90
Purchase #7	$230.64	11.861%	$257.9962	$258.00	$258.00	$258.00
7 purchase totals =	$942.46		$1,032.7385	$1,032.74	$1,032.80	$1,032.80