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	$239.86	10.208%	$264.3449	$264.34	$264.35	$264.30
Purchase #2	$228.37	4.607%	$238.891	$238.89	$238.90	$238.90
Purchase #3	$90.84	4.148%	$94.608	$94.61	$94.60	$94.60
Purchase #4	$169.31	8.828%	$184.2567	$184.26	$184.25	$184.30
Purchase #5	$210.80	7.146%	$225.8638	$225.86	$225.85	$225.90
Purchase #6	$229.28	12.713%	$258.4284	$258.43	$258.45	$258.40
Purchase #7	$191.71	3.412%	$198.2511	$198.25	$198.25	$198.30
7 purchase totals =	$1,360.17		$1,464.6439	$1,464.64	$1,464.65	$1,464.70