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	$246.28	12.447%	$276.9345	$276.93	$276.95	$276.90
Purchase #2	$163.52	5.168%	$171.9707	$171.97	$171.95	$172.00
Purchase #3	$226.63	6.217%	$240.7196	$240.72	$240.70	$240.70
Purchase #4	$92.61	8.639%	$100.6106	$100.61	$100.60	$100.60
Purchase #5	$82.73	9.813%	$90.8483	$90.85	$90.85	$90.80
Purchase #6	$85.26	13.136%	$96.4598	$96.46	$96.45	$96.50
Purchase #7	$115.48	10.178%	$127.2336	$127.23	$127.25	$127.20
7 purchase totals =	$1,012.51		$1,104.7771	$1,104.77	$1,104.75	$1,104.70