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	$73.29	10.749%	$81.1679	$81.17	$81.15	$81.20
Purchase #2	$53.69	6.661%	$57.2663	$57.27	$57.25	$57.30
Purchase #3	$190.87	11.155%	$212.1615	$212.16	$212.15	$212.20
Purchase #4	$80.72	5.530%	$85.1838	$85.18	$85.20	$85.20
Purchase #5	$114.72	5.870%	$121.4541	$121.45	$121.45	$121.50
Purchase #6	$142.29	8.280%	$154.0716	$154.07	$154.05	$154.10
Purchase #7	$30.90	6.831%	$33.0108	$33.01	$33.00	$33.00
7 purchase totals =	$686.48		$744.3160	$744.31	$744.25	$744.50