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	$154.29	4.687%	$161.5216	$161.52	$161.50	$161.50
Purchase #2	$186.71	7.283%	$200.3081	$200.31	$200.30	$200.30
Purchase #3	$81.55	8.835%	$88.7549	$88.75	$88.75	$88.80
Purchase #4	$210.65	3.606%	$218.246	$218.25	$218.25	$218.20
Purchase #5	$25.28	10.218%	$27.8631	$27.86	$27.85	$27.90
Purchase #6	$147.81	9.271%	$161.5135	$161.51	$161.50	$161.50
Purchase #7	$160.57	7.399%	$172.4506	$172.45	$172.45	$172.50
7 purchase totals =	$966.86		$1,030.6578	$1,030.65	$1,030.60	$1,030.70