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	$201.65	11.815%	$225.4749	$225.47	$225.45	$225.50
Purchase #2	$81.96	12.751%	$92.4107	$92.41	$92.40	$92.40
Purchase #3	$198.96	3.221%	$205.3685	$205.37	$205.35	$205.40
Purchase #4	$72.33	11.641%	$80.7499	$80.75	$80.75	$80.70
Purchase #5	$107.40	4.153%	$111.8603	$111.86	$111.85	$111.90
Purchase #6	$157.27	8.363%	$170.4225	$170.42	$170.40	$170.40
Purchase #7	$108.76	8.446%	$117.9459	$117.95	$117.95	$117.90
7 purchase totals =	$928.33		$1,004.2327	$1,004.23	$1,004.15	$1,004.20