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	$155.91	11.552%	$173.9207	$173.92	$173.90	$173.90
Purchase #2	$63.59	12.276%	$71.3963	$71.40	$71.40	$71.40
Purchase #3	$198.92	12.129%	$223.047	$223.05	$223.05	$223.00
Purchase #4	$47.88	10.858%	$53.0788	$53.08	$53.10	$53.10
Purchase #5	$175.95	8.262%	$190.487	$190.49	$190.50	$190.50
Purchase #6	$249.27	3.815%	$258.7797	$258.78	$258.80	$258.80
Purchase #7	$249.54	9.729%	$273.8177	$273.82	$273.80	$273.80
7 purchase totals =	$1,141.06		$1,244.5272	$1,244.54	$1,244.55	$1,244.50