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	$185.39	11.529%	$206.7636	$206.76	$206.75	$206.80
Purchase #2	$169.87	13.541%	$192.8721	$192.87	$192.85	$192.90
Purchase #3	$55.95	8.354%	$60.6241	$60.62	$60.60	$60.60
Purchase #4	$186.53	11.798%	$208.5368	$208.54	$208.55	$208.50
Purchase #5	$180.37	5.228%	$189.7997	$189.80	$189.80	$189.80
Purchase #6	$64.85	5.780%	$68.5983	$68.60	$68.60	$68.60
Purchase #7	$189.47	3.599%	$196.289	$196.29	$196.30	$196.30
7 purchase totals =	$1,032.43		$1,123.4836	$1,123.48	$1,123.45	$1,123.50