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	$212.76	11.675%	$237.5997	$237.60	$237.60	$237.60
Purchase #2	$142.81	6.813%	$152.5396	$152.54	$152.55	$152.50
Purchase #3	$213.37	10.678%	$236.1536	$236.15	$236.15	$236.20
Purchase #4	$95.73	7.742%	$103.1414	$103.14	$103.15	$103.10
Purchase #5	$37.90	7.233%	$40.6413	$40.64	$40.65	$40.60
Purchase #6	$225.94	3.835%	$234.6048	$234.60	$234.60	$234.60
Purchase #7	$207.63	7.261%	$222.706	$222.71	$222.70	$222.70
7 purchase totals =	$1,136.14		$1,227.3864	$1,227.38	$1,227.40	$1,227.30