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	$186.26	5.358%	$196.2398	$196.24	$196.25	$196.20
Purchase #2	$177.64	11.802%	$198.6051	$198.61	$198.60	$198.60
Purchase #3	$79.65	6.253%	$84.6305	$84.63	$84.65	$84.60
Purchase #4	$103.67	12.331%	$116.4535	$116.45	$116.45	$116.50
Purchase #5	$98.44	11.710%	$109.9673	$109.97	$109.95	$110.00
Purchase #6	$235.64	11.773%	$263.3819	$263.38	$263.40	$263.40
Purchase #7	$134.59	4.235%	$140.2899	$140.29	$140.30	$140.30
7 purchase totals =	$1,015.89		$1,109.5680	$1,109.57	$1,109.60	$1,109.60