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	$88.36	6.447%	$94.0566	$94.06	$94.05	$94.10
Purchase #2	$106.40	10.839%	$117.9327	$117.93	$117.95	$117.90
Purchase #3	$73.53	13.613%	$83.5396	$83.54	$83.55	$83.50
Purchase #4	$156.27	7.806%	$168.4684	$168.47	$168.45	$168.50
Purchase #5	$58.64	6.745%	$62.5953	$62.60	$62.60	$62.60
Purchase #6	$142.27	6.543%	$151.5787	$151.58	$151.60	$151.60
Purchase #7	$127.66	12.354%	$143.4311	$143.43	$143.45	$143.40
7 purchase totals =	$753.13		$821.6024	$821.61	$821.65	$821.60