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	$42.41	12.357%	$47.6506	$47.65	$47.65	$47.70
Purchase #2	$73.43	12.539%	$82.6374	$82.64	$82.65	$82.60
Purchase #3	$35.77	4.688%	$37.4469	$37.45	$37.45	$37.40
Purchase #4	$27.51	13.317%	$31.1735	$31.17	$31.15	$31.20
Purchase #5	$198.26	8.127%	$214.3726	$214.37	$214.35	$214.40
Purchase #6	$156.52	6.475%	$166.6547	$166.65	$166.65	$166.70
Purchase #7	$56.85	4.582%	$59.4549	$59.45	$59.45	$59.50
7 purchase totals =	$590.75		$639.3906	$639.38	$639.35	$639.50