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	$61.39	7.141%	$65.7739	$65.77	$65.75	$65.80
Purchase #2	$109.45	12.621%	$123.2637	$123.26	$123.25	$123.30
Purchase #3	$141.79	6.224%	$150.615	$150.62	$150.60	$150.60
Purchase #4	$89.40	5.432%	$94.2562	$94.26	$94.25	$94.30
Purchase #5	$207.36	11.523%	$231.2541	$231.25	$231.25	$231.30
Purchase #6	$50.34	10.707%	$55.7299	$55.73	$55.75	$55.70
Purchase #7	$199.65	6.451%	$212.5294	$212.53	$212.55	$212.50
7 purchase totals =	$859.38		$933.4222	$933.42	$933.40	$933.50