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	$44.58	8.619%	$48.4224	$48.42	$48.40	$48.40
Purchase #2	$236.43	3.558%	$244.8422	$244.84	$244.85	$244.80
Purchase #3	$147.60	3.461%	$152.7084	$152.71	$152.70	$152.70
Purchase #4	$46.89	13.516%	$53.2277	$53.23	$53.25	$53.20
Purchase #5	$70.25	12.183%	$78.8086	$78.81	$78.80	$78.80
Purchase #6	$215.33	11.116%	$239.2661	$239.27	$239.25	$239.30
Purchase #7	$58.87	9.238%	$64.3084	$64.31	$64.30	$64.30
7 purchase totals =	$819.95		$881.5838	$881.59	$881.55	$881.50