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	$169.28	3.779%	$175.6771	$175.68	$175.70	$175.70
Purchase #2	$73.91	6.514%	$78.7245	$78.72	$78.70	$78.70
Purchase #3	$115.41	13.853%	$131.3977	$131.40	$131.40	$131.40
Purchase #4	$229.41	10.381%	$253.2251	$253.23	$253.25	$253.20
Purchase #5	$11.86	6.124%	$12.5863	$12.59	$12.60	$12.60
Purchase #6	$61.72	7.812%	$66.5416	$66.54	$66.55	$66.50
Purchase #7	$187.43	3.646%	$194.2637	$194.26	$194.25	$194.30
7 purchase totals =	$849.02		$912.4160	$912.42	$912.45	$912.40