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	$236.75	10.465%	$261.5259	$261.53	$261.55	$261.50
Purchase #2	$155.65	11.690%	$173.8455	$173.85	$173.85	$173.80
Purchase #3	$167.49	4.397%	$174.8545	$174.85	$174.85	$174.90
Purchase #4	$85.88	4.470%	$89.7188	$89.72	$89.70	$89.70
Purchase #5	$99.75	3.871%	$103.6113	$103.61	$103.60	$103.60
Purchase #6	$62.73	11.458%	$69.9176	$69.92	$69.90	$69.90
Purchase #7	$193.84	7.701%	$208.7676	$208.77	$208.75	$208.80
7 purchase totals =	$1,002.09		$1,082.2412	$1,082.25	$1,082.20	$1,082.20