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	$59.28	13.386%	$67.2152	$67.22	$67.20	$67.20
Purchase #2	$173.53	7.854%	$187.159	$187.16	$187.15	$187.20
Purchase #3	$183.93	6.590%	$196.051	$196.05	$196.05	$196.10
Purchase #4	$125.79	9.124%	$137.2671	$137.27	$137.25	$137.30
Purchase #5	$134.90	4.564%	$141.0568	$141.06	$141.05	$141.10
Purchase #6	$152.47	5.397%	$160.6988	$160.70	$160.70	$160.70
Purchase #7	$249.76	4.679%	$261.4463	$261.45	$261.45	$261.40
7 purchase totals =	$1,079.66		$1,150.8942	$1,150.91	$1,150.85	$1,151.00