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	$189.30	10.384%	$208.9569	$208.96	$208.95	$209.00
Purchase #2	$31.54	9.450%	$34.5205	$34.52	$34.50	$34.50
Purchase #3	$221.59	3.634%	$229.6426	$229.64	$229.65	$229.60
Purchase #4	$160.62	3.872%	$166.8392	$166.84	$166.85	$166.80
Purchase #5	$139.83	5.473%	$147.4829	$147.48	$147.50	$147.50
Purchase #6	$101.26	4.557%	$105.8744	$105.87	$105.85	$105.90
Purchase #7	$210.91	3.108%	$217.4651	$217.47	$217.45	$217.50
7 purchase totals =	$1,055.05		$1,110.7816	$1,110.78	$1,110.75	$1,110.80