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	$92.32	10.371%	$101.8945	$101.89	$101.90	$101.90
Purchase #2	$176.46	10.426%	$194.8577	$194.86	$194.85	$194.90
Purchase #3	$236.77	9.576%	$259.4431	$259.44	$259.45	$259.40
Purchase #4	$145.81	6.142%	$154.7657	$154.77	$154.75	$154.80
Purchase #5	$231.87	5.146%	$243.802	$243.80	$243.80	$243.80
Purchase #6	$122.99	3.478%	$127.2676	$127.27	$127.25	$127.30
Purchase #7	$38.67	10.332%	$42.6654	$42.67	$42.65	$42.70
7 purchase totals =	$1,044.89		$1,124.6960	$1,124.70	$1,124.65	$1,124.80