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	$48.44	11.177%	$53.8541	$53.85	$53.85	$53.90
Purchase #2	$73.96	6.407%	$78.6986	$78.70	$78.70	$78.70
Purchase #3	$218.95	11.668%	$244.4971	$244.50	$244.50	$244.50
Purchase #4	$38.66	7.513%	$41.5645	$41.56	$41.55	$41.60
Purchase #5	$155.87	6.857%	$166.558	$166.56	$166.55	$166.60
Purchase #6	$42.66	10.670%	$47.2118	$47.21	$47.20	$47.20
Purchase #7	$90.41	12.148%	$101.393	$101.39	$101.40	$101.40
7 purchase totals =	$668.95		$733.7771	$733.77	$733.75	$733.90