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	$52.39	5.480%	$55.261	$55.26	$55.25	$55.30
Purchase #2	$93.59	5.327%	$98.5755	$98.58	$98.60	$98.60
Purchase #3	$161.70	10.560%	$178.7755	$178.78	$178.80	$178.80
Purchase #4	$86.96	3.371%	$89.8914	$89.89	$89.90	$89.90
Purchase #5	$86.52	12.840%	$97.6292	$97.63	$97.65	$97.60
Purchase #6	$101.35	10.403%	$111.8934	$111.89	$111.90	$111.90
Purchase #7	$18.53	11.443%	$20.6504	$20.65	$20.65	$20.70
7 purchase totals =	$601.04		$652.6764	$652.68	$652.75	$652.80