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	$55.98	11.780%	$62.5744	$62.57	$62.55	$62.60
Purchase #2	$179.72	11.419%	$200.2422	$200.24	$200.25	$200.20
Purchase #3	$160.80	8.185%	$173.9615	$173.96	$173.95	$174.00
Purchase #4	$216.64	10.259%	$238.8651	$238.87	$238.85	$238.90
Purchase #5	$158.96	5.506%	$167.7123	$167.71	$167.70	$167.70
Purchase #6	$67.49	5.301%	$71.0676	$71.07	$71.05	$71.10
Purchase #7	$70.80	10.308%	$78.0981	$78.10	$78.10	$78.10
7 purchase totals =	$910.39		$992.5212	$992.52	$992.45	$992.60