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	$86.31	8.615%	$93.7456	$93.75	$93.75	$93.70
Purchase #2	$142.38	13.404%	$161.4646	$161.46	$161.45	$161.50
Purchase #3	$203.84	10.173%	$224.5766	$224.58	$224.60	$224.60
Purchase #4	$177.56	8.192%	$192.1057	$192.11	$192.10	$192.10
Purchase #5	$29.72	12.693%	$33.4924	$33.49	$33.50	$33.50
Purchase #6	$116.98	10.152%	$128.8558	$128.86	$128.85	$128.90
Purchase #7	$211.59	10.524%	$233.8577	$233.86	$233.85	$233.90
7 purchase totals =	$968.38		$1,068.0984	$1,068.11	$1,068.10	$1,068.20