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	$53.97	10.427%	$59.5975	$59.60	$59.60	$59.60
Purchase #2	$107.71	4.213%	$112.2478	$112.25	$112.25	$112.20
Purchase #3	$127.64	4.700%	$133.6391	$133.64	$133.65	$133.60
Purchase #4	$159.33	4.532%	$166.5508	$166.55	$166.55	$166.60
Purchase #5	$93.89	12.837%	$105.9427	$105.94	$105.95	$105.90
Purchase #6	$57.52	6.606%	$61.3198	$61.32	$61.30	$61.30
Purchase #7	$50.37	3.681%	$52.2241	$52.22	$52.20	$52.20
7 purchase totals =	$650.43		$691.5218	$691.52	$691.50	$691.40