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	$62.27	3.623%	$64.526	$64.53	$64.55	$64.50
Purchase #2	$96.35	9.626%	$105.6247	$105.62	$105.60	$105.60
Purchase #3	$170.97	4.341%	$178.3918	$178.39	$178.40	$178.40
Purchase #4	$214.78	7.685%	$231.2858	$231.29	$231.30	$231.30
Purchase #5	$115.80	3.530%	$119.8877	$119.89	$119.90	$119.90
Purchase #6	$145.31	8.367%	$157.4681	$157.47	$157.45	$157.50
Purchase #7	$228.63	5.103%	$240.297	$240.30	$240.30	$240.30
7 purchase totals =	$1,034.11		$1,097.4811	$1,097.49	$1,097.50	$1,097.50