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	12.268%	$60.591	$60.59	$60.60	$60.60
Purchase #2	$39.55	9.661%	$43.3709	$43.37	$43.35	$43.40
Purchase #3	$218.68	4.367%	$228.2298	$228.23	$228.25	$228.20
Purchase #4	$50.54	7.223%	$54.1905	$54.19	$54.20	$54.20
Purchase #5	$50.91	5.252%	$53.5838	$53.58	$53.60	$53.60
Purchase #6	$235.72	3.204%	$243.2725	$243.27	$243.25	$243.30
Purchase #7	$204.25	7.336%	$219.2338	$219.23	$219.25	$219.20
7 purchase totals =	$853.62		$902.4723	$902.46	$902.50	$902.50