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	$146.89	3.246%	$151.658	$151.66	$151.65	$151.70
Purchase #2	$31.30	6.137%	$33.2209	$33.22	$33.20	$33.20
Purchase #3	$223.79	6.499%	$238.3341	$238.33	$238.35	$238.30
Purchase #4	$132.37	10.361%	$146.0849	$146.08	$146.10	$146.10
Purchase #5	$230.40	3.459%	$238.3695	$238.37	$238.35	$238.40
Purchase #6	$249.88	4.571%	$261.302	$261.30	$261.30	$261.30
Purchase #7	$11.65	5.326%	$12.2705	$12.27	$12.25	$12.30
7 purchase totals =	$1,026.28		$1,081.2399	$1,081.23	$1,081.20	$1,081.30