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	$149.61	8.594%	$162.4675	$162.47	$162.45	$162.50
Purchase #2	$70.94	11.706%	$79.2442	$79.24	$79.25	$79.20
Purchase #3	$59.55	5.247%	$62.6746	$62.67	$62.65	$62.70
Purchase #4	$57.28	11.385%	$63.8013	$63.80	$63.80	$63.80
Purchase #5	$167.71	12.482%	$188.6436	$188.64	$188.65	$188.60
Purchase #6	$246.53	3.793%	$255.8809	$255.88	$255.90	$255.90
Purchase #7	$166.86	7.639%	$179.6064	$179.61	$179.60	$179.60
7 purchase totals =	$918.48		$992.3185	$992.31	$992.30	$992.30