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	$154.28	11.213%	$171.5794	$171.58	$171.60	$171.60
Purchase #2	$224.43	3.809%	$232.9785	$232.98	$233.00	$233.00
Purchase #3	$138.78	12.830%	$156.5855	$156.59	$156.60	$156.60
Purchase #4	$123.44	10.509%	$136.4123	$136.41	$136.40	$136.40
Purchase #5	$144.41	9.670%	$158.3744	$158.37	$158.35	$158.40
Purchase #6	$38.61	9.251%	$42.1818	$42.18	$42.20	$42.20
Purchase #7	$188.89	8.855%	$205.6162	$205.62	$205.60	$205.60
7 purchase totals =	$1,012.84		$1,103.7281	$1,103.73	$1,103.75	$1,103.80