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	$161.29	4.516%	$168.5739	$168.57	$168.55	$168.60
Purchase #2	$166.66	9.261%	$182.0944	$182.09	$182.10	$182.10
Purchase #3	$111.39	10.736%	$123.3488	$123.35	$123.35	$123.30
Purchase #4	$172.43	7.734%	$185.7657	$185.77	$185.75	$185.80
Purchase #5	$230.80	9.428%	$252.5598	$252.56	$252.55	$252.60
Purchase #6	$115.32	5.211%	$121.3293	$121.33	$121.35	$121.30
Purchase #7	$59.73	11.782%	$66.7674	$66.77	$66.75	$66.80
7 purchase totals =	$1,017.62		$1,100.4393	$1,100.44	$1,100.40	$1,100.50