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	$117.89	8.245%	$127.61	$127.61	$127.60	$127.60
Purchase #2	$21.80	8.820%	$23.7228	$23.72	$23.70	$23.70
Purchase #3	$153.69	10.459%	$169.7644	$169.76	$169.75	$169.80
Purchase #4	$35.77	12.452%	$40.2241	$40.22	$40.20	$40.20
Purchase #5	$240.80	8.489%	$261.2415	$261.24	$261.25	$261.20
Purchase #6	$199.88	7.714%	$215.2987	$215.30	$215.30	$215.30
Purchase #7	$166.44	7.866%	$179.5322	$179.53	$179.55	$179.50
7 purchase totals =	$936.27		$1,017.3937	$1,017.38	$1,017.35	$1,017.30