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	$122.37	8.244%	$132.4582	$132.46	$132.45	$132.50
Purchase #2	$174.78	12.361%	$196.3846	$196.38	$196.40	$196.40
Purchase #3	$194.96	10.311%	$215.0623	$215.06	$215.05	$215.10
Purchase #4	$122.65	6.212%	$130.269	$130.27	$130.25	$130.30
Purchase #5	$182.72	3.122%	$188.4245	$188.42	$188.40	$188.40
Purchase #6	$143.79	6.649%	$153.3506	$153.35	$153.35	$153.40
Purchase #7	$93.79	6.504%	$99.8901	$99.89	$99.90	$99.90
7 purchase totals =	$1,035.06		$1,115.8393	$1,115.83	$1,115.80	$1,116.00