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	$248.86	7.171%	$266.7058	$266.71	$266.70	$266.70
Purchase #2	$139.38	9.475%	$152.5863	$152.59	$152.60	$152.60
Purchase #3	$86.98	3.148%	$89.7181	$89.72	$89.70	$89.70
Purchase #4	$181.70	7.345%	$195.0459	$195.05	$195.05	$195.00
Purchase #5	$191.55	13.729%	$217.8479	$217.85	$217.85	$217.80
Purchase #6	$240.25	5.636%	$253.7905	$253.79	$253.80	$253.80
Purchase #7	$172.32	7.495%	$185.2354	$185.24	$185.25	$185.20
7 purchase totals =	$1,261.04		$1,360.9299	$1,360.95	$1,360.95	$1,360.80