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	$209.38	5.465%	$220.8226	$220.82	$220.80	$220.80
Purchase #2	$160.32	7.530%	$172.3921	$172.39	$172.40	$172.40
Purchase #3	$90.74	13.772%	$103.2367	$103.24	$103.25	$103.20
Purchase #4	$199.48	4.502%	$208.4606	$208.46	$208.45	$208.50
Purchase #5	$177.70	10.812%	$196.9129	$196.91	$196.90	$196.90
Purchase #6	$106.99	8.159%	$115.7193	$115.72	$115.70	$115.70
Purchase #7	$69.94	13.794%	$79.5875	$79.59	$79.60	$79.60
7 purchase totals =	$1,014.55		$1,097.1317	$1,097.13	$1,097.10	$1,097.10