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	$178.36	9.672%	$195.611	$195.61	$195.60	$195.60
Purchase #2	$126.94	12.406%	$142.6882	$142.69	$142.70	$142.70
Purchase #3	$38.74	9.503%	$42.4215	$42.42	$42.40	$42.40
Purchase #4	$229.78	10.208%	$253.2359	$253.24	$253.25	$253.20
Purchase #5	$69.90	4.264%	$72.8805	$72.88	$72.90	$72.90
Purchase #6	$92.94	8.753%	$101.075	$101.08	$101.10	$101.10
Purchase #7	$79.65	3.400%	$82.3581	$82.36	$82.35	$82.40
7 purchase totals =	$816.31		$890.2702	$890.28	$890.30	$890.30