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	$157.30	13.645%	$178.7636	$178.76	$178.75	$178.80
Purchase #2	$78.72	13.813%	$89.5936	$89.59	$89.60	$89.60
Purchase #3	$34.94	5.863%	$36.9885	$36.99	$37.00	$37.00
Purchase #4	$101.45	3.409%	$104.9084	$104.91	$104.90	$104.90
Purchase #5	$17.37	9.167%	$18.9623	$18.96	$18.95	$19.00
Purchase #6	$98.55	3.517%	$102.016	$102.02	$102.00	$102.00
Purchase #7	$19.95	6.568%	$21.2603	$21.26	$21.25	$21.30
7 purchase totals =	$508.28		$552.4927	$552.49	$552.45	$552.60