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	$163.85	9.209%	$178.9389	$178.94	$178.95	$178.90
Purchase #2	$163.42	9.614%	$179.1312	$179.13	$179.15	$179.10
Purchase #3	$147.91	9.218%	$161.5443	$161.54	$161.55	$161.50
Purchase #4	$28.53	7.841%	$30.767	$30.77	$30.75	$30.80
Purchase #5	$231.68	9.610%	$253.9444	$253.94	$253.95	$253.90
Purchase #6	$40.25	5.228%	$42.3543	$42.35	$42.35	$42.40
Purchase #7	$161.87	6.739%	$172.7784	$172.78	$172.80	$172.80
7 purchase totals =	$937.51		$1,019.4585	$1,019.45	$1,019.50	$1,019.40